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Message-ID: <ZjAueNMN8nSbsqvI@pengutronix.de>
Date: Tue, 30 Apr 2024 01:34:16 +0200
From: Michael Grzeschik <mgr@...gutronix.de>
To: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Cc: Eric Van Hensbergen <ericvh@...nel.org>,
Latchesar Ionkov <lucho@...kov.net>,
Dominique Martinet <asmadeus@...ewreck.org>,
Christian Schoenebeck <linux_oss@...debyte.com>,
Jonathan Corbet <corbet@....net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
v9fs@...ts.linux.dev, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel@...gutronix.de,
linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 2/3] net/9p/usbg: Add new usb gadget function transport
Hi Andrzej!
Based on your feedback I rolled out v4.
https://lore.kernel.org/r/20240116-ml-topic-u9p-v4-0-722ed28b0ade@pengutronix.de
On Wed, Mar 06, 2024 at 04:18:54PM +0100, Andrzej Pietrasiewicz wrote:
>W dniu 26.02.2024 o 14:56, Michael Grzeschik pisze:
>>Add the new gadget function for 9pfs transport. This function is
>>defining an simple 9pfs transport interface that consists of one in and
>>one out endpoint. The endpoints transmit and receive the 9pfs protocol
>>payload when mounting a 9p filesystem over usb.
>
>Reading the earlier discussions on v1 and v2 I was somehow under the impression
>that what you submitted here does not contain configfs support.
>
>But once I started reading the code I realized it does.
>
>It worked for me, both as a legacy gadget and when composed with configfs.
>
>I noticed that when you stop the forwarder at the host side when 9pfs remains
>mounted at the gadget side, umount hangs at the gadget side until the forwarder
>is restarted. I know that once the host-side software dies, not much can be
>done, however, unmounting a dead filesystem seems a reasonable thing to do
>and the way usb9pfs worked for me it is not possible to unmount in this
>situation. Any ideas on improving this?
As Dominique suggested I implemented conn_cancel to ensure the
connection to be removed on the gadget side. Regarding the stopped
correspondence from the host-side, there is not much we can do.
However for the v4 I ensured that a mount -f would work out
by checking the connection status before sending anything
to the host.
With this changes I was able to mount and unmount several times
and always reuse the gadget connection by restarting the host side.
>Please find my review below.
>
>>
>>Signed-off-by: Michael Grzeschik <m.grzeschik@...gutronix.de>
>>
>>---
>>v2 -> v3: -
>>v1 -> v2:
>> - move the driver to net/9p/trans_usbg.c
>> - fixed the commit title
>> - fix %zu usage in p9_debug for size_t type
>> - define functions static that are only used localy
>> - return 0 in alloc_requests
>> - use id_alloc_max instead of ida_simple_get
>> - call ida_free in usb9pfs_free_func
>> - call kfree for usb9pfs->tag and usb9pfs in usb9pfs_free_func
>> - add MODULE_ALIAS_9P to load this module automatic when mounting
>> - improved the documentation
>> - added depends on USB_GADGET in Kconfig
>>---
>> Documentation/filesystems/9p.rst | 15 +
>> net/9p/Kconfig | 6 +
>> net/9p/Makefile | 4 +
>> net/9p/trans_usbg.c | 871 +++++++++++++++++++++++++++++++++++++++
>> 4 files changed, 896 insertions(+)
>>
>>diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst
>>index 1e0e0bb6fdf91..64439068a8fc5 100644
>>--- a/Documentation/filesystems/9p.rst
>>+++ b/Documentation/filesystems/9p.rst
>>@@ -53,6 +53,20 @@ mount points. Each 9P export is seen by the client as a virtio device with an
>> associated "mount_tag" property. Available mount tags can be
>> seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
>>+USBG Usage
>>+==========
>>+
>>+To mount a 9p FS on a USB Host accessible via the gadget at runtime::
>>+
>>+ mount -t 9p -o trans=usbg,aname=/path/to/fs <mount_tag> /mnt/9
>>+
>>+To mount a 9p FS on a USB Host accessible via the gadget as root filesystem::
>>+
>>+ root=<mount_tag> rootfstype=9p rootflags=trans=usbg,cache=loose,uname=root,access=0,dfltuid=0,dfltgid=0,aname=/path/to/rootfs
>>+
>>+where mount_tag is the tag associated by the usb gadget transport. The
>>+pattern is usb9pfs0, usb9pfs1, ...
>
>I'd reword to use "generated" instead of "associated" which would emphasize
>that it is the usb gadget transport part that comes up with the name.
>The word "associated" suggests that maybe the name comes from elsewhere.
>
>I'm wondering if it would make sense to treat instance name, e.g.
>
>"my_9pfs" from
>
>$ mkdir /sys/kernel/config/usb_gadget/g9pfs/functions/usb9pfs.my_9pfs
>
>as device name known above as "<mount_tag>?"
>
>FunctionFS uses this strategy and IMO it makes sense to follow this pattern.
>
>BTW, isn't this being called "mount_tag" an implementation detail of 9pfs?
>When doing "mount" users usually expect a "device name" (even if not a "real"
>device).
Fair point about the mount_tag. I reworked it to be used like with ffs.
>>+
>> Options
>> =======
>>@@ -68,6 +82,7 @@ Options
>> virtio connect to the next virtio channel available
>> (from QEMU with trans_virtio module)
>> rdma connect to a specified RDMA channel
>>+ usbg connect to a specified usb gadget channel
>> ======== ============================================
>> uname=name user name to attempt mount as on the remote server. The
>>diff --git a/net/9p/Kconfig b/net/9p/Kconfig
>>index 00ebce9e5a657..c3d357eb8bb37 100644
>>--- a/net/9p/Kconfig
>>+++ b/net/9p/Kconfig
>>@@ -39,6 +39,12 @@ config NET_9P_XEN
>> This builds support for a transport for 9pfs between
>> two Xen domains.
>>+config NET_9P_USBG
>>+ bool "9P USB Gadget Transport"
>>+ depends on USB_GADGET
>>+ help
>>+ This builds support for a transport for 9pfs over
>>+ usb gadget.
>> config NET_9P_RDMA
>> depends on INET && INFINIBAND && INFINIBAND_ADDR_TRANS
>>diff --git a/net/9p/Makefile b/net/9p/Makefile
>>index 1df9b344c30bd..22794a451c3f7 100644
>>--- a/net/9p/Makefile
>>+++ b/net/9p/Makefile
>>@@ -4,6 +4,7 @@ obj-$(CONFIG_NET_9P_FD) += 9pnet_fd.o
>> obj-$(CONFIG_NET_9P_XEN) += 9pnet_xen.o
>> obj-$(CONFIG_NET_9P_VIRTIO) += 9pnet_virtio.o
>> obj-$(CONFIG_NET_9P_RDMA) += 9pnet_rdma.o
>>+obj-$(CONFIG_NET_9P_USBG) += 9pnet_usbg.o
>> 9pnet-objs := \
>> mod.o \
>>@@ -23,3 +24,6 @@ obj-$(CONFIG_NET_9P_RDMA) += 9pnet_rdma.o
>> 9pnet_rdma-objs := \
>> trans_rdma.o \
>>+
>>+9pnet_usbg-objs := \
>>+ trans_usbg.o \
>>diff --git a/net/9p/trans_usbg.c b/net/9p/trans_usbg.c
>>new file mode 100644
>>index 0000000000000..93d9606a806d8
>>--- /dev/null
>>+++ b/net/9p/trans_usbg.c
>>@@ -0,0 +1,871 @@
>>+// SPDX-License-Identifier: GPL-2.0+
>>+/*
>>+ * trans_usbg.c - USB peripheral usb9pfs configuration driver and transport.
>>+ *
>>+ * Copyright (C) 2024 Michael Grzeschik <m.grzeschik@...gutronix.de>
>>+ */
>>+
>>+/* Gadget usb9pfs only needs two bulk endpoints, and will use the usb9pfs
>>+ * transport to mount host exported filesystem via usb gadget.
>>+ */
>>+
>>+/* +--------------------------+ | +--------------------------+
>>+ * | 9PFS mounting client | | | 9PFS exporting server |
>>+ * SW | | | | |
>>+ * | (this:trans_usbg) | | |(e.g. diod or nfs-ganesha)|
>>+ * +-------------^------------+ | +-------------^------------+
>>+ * | | |
>>+ * ------------------|------------------------------------|-------------
>>+ * | | |
>>+ * +-------------v------------+ | +-------------v------------+
>>+ * | | | | |
>>+ * HW | USB Device Controller <---------> USB Host Controller |
>>+ * | | | | |
>>+ * +--------------------------+ | +--------------------------+
>>+ */
>>+
>>+#include <linux/slab.h>
>>+#include <linux/kernel.h>
>>+#include <linux/device.h>
>>+#include <linux/module.h>
>>+#include <linux/err.h>
>>+#include <linux/usb/composite.h>
>>+#include <linux/usb/u_f.h>
>>+
>>+#include <net/9p/9p.h>
>>+#include <net/9p/client.h>
>>+#include <net/9p/transport.h>
>>+
>>+#define DEFAULT_BUFLEN 16384
>>+
>>+struct f_usb9pfs {
>>+ struct p9_client *client;
>>+
>>+ struct p9_req_t *p9_tx_req;
>>+
>>+ struct list_head tx_req_list;
>>+
>>+ /* 9p request lock for en/dequeue */
>>+ spinlock_t lock;
>>+ /* usb request lock for en/dequeue */
>>+ spinlock_t req_lock;
>>+
>>+ struct usb_request *in_req;
>>+ struct usb_request *out_req;
>>+
>>+ struct usb_ep *in_ep;
>>+ struct usb_ep *out_ep;
>>+
>>+ unsigned int buflen;
>>+
>>+ bool inuse;
>>+ char *tag;
>>+
>>+ int index;
>>+
>>+ struct usb_function function;
>>+
>>+ struct list_head function_list;
>
>usb9pfs_instance ?
Sounds good. I changed it.
>>+};
>>+
>>+static inline struct f_usb9pfs *func_to_usb9pfs(struct usb_function *f)
>>+{
>>+ return container_of(f, struct f_usb9pfs, function);
>>+}
>>+
>>+struct f_usb9pfs_opts {
>>+ struct usb_function_instance func_inst;
>>+ unsigned int buflen;
>>+
>>+ /* Read/write access to configfs attributes is handled by configfs.
>>+ *
>>+ * This is to protect the data from concurrent access by read/write
>>+ * and create symlink/remove symlink.
>>+ */
>>+ struct mutex lock;
>>+ int refcnt;
>>+};
>>+
>>+static DEFINE_IDA(usb9pfs_ida);
>>+static DEFINE_MUTEX(usb9pfs_ida_lock); /* protects access do usb9pfs_ida */
>>+
>>+static DEFINE_MUTEX(usb9pfs_lock);
>>+static struct list_head usbg_function_list;
>
>This name seems too generic to me, it creates an impression that the list
>contains all functions of USB gadgets. It really doesn't and what it
>contains is a number of 9pfs instances. What about usb9pfs_instance_list?
I will go with usb9pfs_instance_list.
>>+
>>+static int usb9pfs_tx_fill(struct f_usb9pfs *usb9pfs, struct usb_request *req,
>
>given what this function effectively does...
>
>>+ gfp_t gfp_flags)
>>+{
>>+ struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
>>+ int retval = -ENOMEM;
>>+
>>+ if (!(usb9pfs->p9_tx_req->tc.size % usb9pfs->in_ep->maxpacket))
>>+ req->zero = 1;
>>+
>>+ req->buf = usb9pfs->p9_tx_req->tc.sdata;
>>+ req->length = usb9pfs->p9_tx_req->tc.size;
>>+
>>+ dev_dbg(&cdev->gadget->dev, "%s usb9pfs send --> %d/%d, zero: %d\n",
>>+ usb9pfs->in_ep->name, req->actual, req->length, req->zero);
>>+
>>+ retval = usb_ep_queue(usb9pfs->in_ep, req, gfp_flags);
>
>... (which is usb_ep_queue), I'd rather name it e.g. usb9pfs_tx_queue.
>Or maybe usb9pfs_queue_tx to not create an impression that the function
>is a queue of some sort (because rather than being a queue it does queueing).
I changed it to usb9pfs_queue_tx.
>>+
>>+ dev_dbg(&cdev->gadget->dev, "tx submit --> %d\n", retval);
>>+
>>+ return retval;
>>+}
>
>The return value of this function is never used.
Right, I fixed that at each caller.
>
>>+
>>+static int usb9pfs_rx_fill(struct f_usb9pfs *usb9pfs, struct usb_request *req,
>
>usb9pfs_queue_rx() ?
I changed it to usb9pfs_queue_rx.
>>+ gfp_t gfp_flags)
>>+{
>>+ struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
>>+ int retval = -ENOMEM;
>>+
>>+ retval = usb_ep_queue(usb9pfs->out_ep, req, gfp_flags);
>>+
>>+ dev_dbg(&cdev->gadget->dev, "rx submit --> %d\n", retval);
>>+
>>+ return retval;
>>+}
>
>The return value of this function is never used.
Right, I fixed that at each caller.
>>+
>>+static int usb9pfs_transmit(struct f_usb9pfs *usb9pfs)
>
>Might be worth documenting that this needs to be called with req_lock held.
I wrote a comment above the function name.
>>+{
>>+ struct p9_req_t *p9_req = NULL;
>>+ unsigned long flags;
>>+ int ret = 0;
>>+
>>+ spin_lock_irqsave(&usb9pfs->lock, flags);
>>+
>>+ if (usb9pfs->p9_tx_req) {
>>+ spin_unlock_irqrestore(&usb9pfs->lock, flags);
>>+ return -EBUSY;
>>+ }
>>+
>>+ p9_req = list_first_entry_or_null(&usb9pfs->tx_req_list, struct p9_req_t, req_list);
>>+ if (!p9_req) {
>>+ spin_unlock_irqrestore(&usb9pfs->lock, flags);
>>+ return -ENOENT;
>>+ }
>>+
>>+ list_del(&p9_req->req_list);
>>+
>>+ usb9pfs->p9_tx_req = p9_req;
>>+
>>+ p9_req_get(usb9pfs->p9_tx_req);
>>+
>>+ usb9pfs_tx_fill(usb9pfs, usb9pfs->in_req, GFP_ATOMIC);
>>+
>>+ spin_unlock_irqrestore(&usb9pfs->lock, flags);
>>+
>>+ return ret;
>>+}
>>+
>>+static void usb9pfs_tx_complete(struct usb_ep *ep, struct usb_request *req)
>>+{
>>+ struct f_usb9pfs *usb9pfs = ep->driver_data;
>>+ struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
>>+
>>+ /* reset zero packages */
>>+ req->zero = 0;
>>+
>>+ dev_dbg(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n",
>>+ ep->name, req->status, req->actual, req->length);
>>+
>>+ switch (req->status) {
>
>Are more cases expected here? I'm asking because for now it seems
>that "if - else" would do the job.
You are right if else is doing the job just well. I changed it.
>>+ case 0: /* normal completion? */
>>+ spin_lock(&usb9pfs->req_lock);
>>+
>>+ WRITE_ONCE(usb9pfs->p9_tx_req->status, REQ_STATUS_SENT);
>>+
>>+ p9_req_put(usb9pfs->client, usb9pfs->p9_tx_req);
>>+
>>+ usb9pfs_rx_fill(usb9pfs, usb9pfs->out_req, GFP_ATOMIC);
>>+
>>+ spin_unlock(&usb9pfs->req_lock);
>>+
>>+ break;
>>+
>>+ default:
>>+ dev_err(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n",
>>+ ep->name, req->status, req->actual, req->length);
>>+ usb_ep_free_request(ep == usb9pfs->in_ep ?
>>+ usb9pfs->out_ep : usb9pfs->in_ep,
>>+ req->context);
>>+ free_ep_req(ep, req);
>>+ return;
>
>Is this return necessary? The "default" branch does contain some statements,
>so there's no need to silence the compiler.
I removed it.
>>+ }
>>+}
>>+
>>+static struct p9_req_t *usb9pfs_rx_header(struct f_usb9pfs *usb9pfs,
>>+ struct usb_request *req)
>
>It seems that the logic of this function does not depend on anything USB.
>It is all p9 stuff, so I'd rather accept a plain buffer instead of usb_request.
Good point. I moved it to use the plain buffer instead.
>>+{
>>+ struct p9_req_t *p9_rx_req;
>>+ struct p9_fcall rc;
>>+ int ret;
>>+
>>+ /* start by reading header */
>>+ rc.sdata = req->buf;
>>+ rc.offset = 0;
>>+ rc.capacity = P9_HDRSZ;
>>+ rc.size = P9_HDRSZ;
>>+
>>+ p9_debug(P9_DEBUG_TRANS, "mux %p got %zu bytes\n", usb9pfs,
>>+ rc.capacity - rc.offset);
>>+
>>+ ret = p9_parse_header(&rc, &rc.size, NULL, NULL, 0);
>>+ if (ret) {
>>+ p9_debug(P9_DEBUG_ERROR,
>>+ "error parsing header: %d\n", ret);
>>+ return NULL;
>>+ }
>>+
>>+ p9_debug(P9_DEBUG_TRANS,
>>+ "mux %p pkt: size: %d bytes tag: %d\n",
>>+ usb9pfs, rc.size, rc.tag);
>>+
>>+ p9_rx_req = p9_tag_lookup(usb9pfs->client, rc.tag);
>>+ if (!p9_rx_req || p9_rx_req->status != REQ_STATUS_SENT) {
>>+ p9_debug(P9_DEBUG_ERROR, "Unexpected packet tag %d\n", rc.tag);
>>+ return NULL;
>>+ }
>>+
>
>I know nothing about p9 proper, but it seems that at this point
>you have p9_rx_req...
>
>>+ if (rc.size > p9_rx_req->rc.capacity) {
>>+ p9_debug(P9_DEBUG_ERROR,
>>+ "requested packet size too big: %d for tag %d with capacity %zd\n",
>>+ rc.size, rc.tag, p9_rx_req->rc.capacity);
>>+ return NULL;
>
>... which you don't "put" here, but...
Nice catch. I added p9_req_put here aswell.
>>+ }
>>+
>>+ if (!p9_rx_req->rc.sdata) {
>>+ p9_debug(P9_DEBUG_ERROR,
>>+ "No recv fcall for tag %d (req %p), disconnecting!\n",
>>+ rc.tag, p9_rx_req);
>>+ p9_req_put(usb9pfs->client, p9_rx_req);
>
>... you do "put" it here. Not sure if this is ok or not ok, just asking,
>because judging by the return value the caller of this function seems unable
>to know which of the above "return" statements caused a NULL, hence it is
>unable to tell whether it (the caller) should "put" or not.
>
>>+ return NULL;
>>+ }
>>+
>>+ return p9_rx_req;
>>+}
>>+
>>+static void usb9pfs_rx_complete(struct usb_ep *ep, struct usb_request *req)
>>+{
>>+ struct f_usb9pfs *usb9pfs = ep->driver_data;
>>+ struct usb_composite_dev *cdev = usb9pfs->function.config->cdev;
>>+ struct p9_req_t *p9_rx_req;
>>+ unsigned long flags;
>>+
>>+ switch (req->status) {
>>+ case 0: /* normal completion? */
>>+ spin_lock_irqsave(&usb9pfs->req_lock, flags);
>>+ p9_rx_req = usb9pfs_rx_header(usb9pfs, req);
>>+ if (!p9_rx_req) {
>>+ spin_unlock_irqrestore(&usb9pfs->req_lock, flags);
>>+ goto free_req;
>>+ }
>>+
>>+ memcpy(p9_rx_req->rc.sdata, req->buf, req->actual);
>>+ p9_rx_req->rc.size = req->actual;
>>+
>>+ p9_client_cb(usb9pfs->client, p9_rx_req, REQ_STATUS_RCVD);
>>+ p9_req_put(usb9pfs->client, p9_rx_req);
>>+
>>+ usb9pfs->p9_tx_req = NULL;
>>+
>>+ usb9pfs_transmit(usb9pfs);
>>+
>>+ spin_unlock_irqrestore(&usb9pfs->req_lock, flags);
>>+
>>+ return;
>>+free_req:
>>+ default:
>>+ dev_err(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n",
>>+ ep->name, req->status, req->actual, req->length);
>>+ usb_ep_free_request(ep == usb9pfs->in_ep ?
>>+ usb9pfs->out_ep : usb9pfs->in_ep,
>>+ req->context);
>>+ free_ep_req(ep, req);
>>+ return;
>
>I assume this return means that p9_client_cb() should not be called if
>either "free_req" or "default" cases happen?
>
>But then anything after the end of this "switch" instruction seems unreachable
>code.
Right, it was some leftover. I removed the p9_client_cb.
>>+ }
>>+
>>+ p9_client_cb(usb9pfs->client, p9_rx_req, REQ_STATUS_ERROR);
>>+}
>>+
>>+static void disable_ep(struct usb_composite_dev *cdev, struct usb_ep *ep)
>>+{
>>+ int value;
>>+
>>+ value = usb_ep_disable(ep);
>>+ if (value < 0)
>>+ dev_info(&cdev->gadget->dev, "disable %s --> %d\n", ep->name, value);
>>+}
>>+
>>+static void disable_endpoints(struct usb_composite_dev *cdev,
>>+ struct usb_ep *in, struct usb_ep *out,
>>+ struct usb_ep *iso_in, struct usb_ep *iso_out)
>
>iso_in and iso_out are never used
>
>>+{
>>+ disable_ep(cdev, in);
>>+ disable_ep(cdev, out);
>
>I'm not sure how useful this whole function is...
>
>>+}
>>+
>>+static void disable_usb9pfs(struct f_usb9pfs *usb9pfs)
>>+{
>>+ struct usb_composite_dev *cdev;
>>+
>>+ cdev = usb9pfs->function.config->cdev;
>>+ disable_endpoints(cdev, usb9pfs->in_ep, usb9pfs->out_ep, NULL, NULL);
>
>... why not
> disable_ep(cdev, usb9pfs->in_ep);
> disable_ep(cdev, usb9pfs->out_ep);
>?
I removed the function and use the disable calls directly.
>>+ dev_dbg(&cdev->gadget->dev, "%s disabled\n", usb9pfs->function.name);
>>+}
>>+
>>+static inline struct usb_request *usb9pfs_alloc_ep_req(struct usb_ep *ep, int len)
>>+{
>>+ return alloc_ep_req(ep, len);
>>+}
>
>What is the purpose of this wrapper?
Leftover from some copy paste section. I removed it.
>>+
>>+static int alloc_requests(struct usb_composite_dev *cdev,
>>+ struct f_usb9pfs *usb9pfs)
>>+{
>>+ usb9pfs->in_req = usb_ep_alloc_request(usb9pfs->in_ep, GFP_ATOMIC);
>>+ if (!usb9pfs->in_req)
>>+ goto fail;
>>+
>>+ usb9pfs->out_req = usb9pfs_alloc_ep_req(usb9pfs->out_ep, usb9pfs->buflen);
>>+ if (!usb9pfs->out_req)
>>+ goto fail_in;
>>+
>>+ usb9pfs->in_req->complete = usb9pfs_tx_complete;
>>+ usb9pfs->out_req->complete = usb9pfs_rx_complete;
>>+
>>+ /* length will be set in complete routine */
>>+ usb9pfs->in_req->context = usb9pfs;
>>+ usb9pfs->out_req->context = usb9pfs;
>>+
>>+ return 0;
>>+
>>+fail_in:
>>+ usb_ep_free_request(usb9pfs->in_ep, usb9pfs->in_req);
>>+fail:
>>+ return 0;
>>+}
>
>This funcion returns a zero no matter what. Such a return value carries
>no information. I saw something in the changelog regarding returning 0,
>was it about this function? But then why return always 0 instead of void?
I changed it to proper return values.
>>+
>>+static int enable_endpoint(struct usb_composite_dev *cdev,
>>+ struct f_usb9pfs *usb9pfs, struct usb_ep *ep)
>>+{
>>+ int result;
>>+
>>+ result = config_ep_by_speed(cdev->gadget, &usb9pfs->function, ep);
>>+ if (result)
>>+ goto out;
>>+
>>+ result = usb_ep_enable(ep);
>>+ if (result < 0)
>>+ goto out;
>>+
>>+ ep->driver_data = usb9pfs;
>>+
>>+ result = 0;
>>+
>>+out:
>>+ return result;
>
>I assume this is "a single point of return". You'd save 3 lines of code
>by returning "result" on the spot instead of gotos and explicitly
>returning a zero. Who knows, maybe modern compilers are smart enough
>to figure this out. Not a deal breaker for me, though.
I squashed it as you suggested.
>>+}
>>+
>>+static int
>>+enable_usb9pfs(struct usb_composite_dev *cdev, struct f_usb9pfs *usb9pfs)
>>+{
>>+ int result = 0;
>>+
>>+ result = enable_endpoint(cdev, usb9pfs, usb9pfs->in_ep);
>>+ if (result)
>>+ goto out;
>>+
>>+ result = enable_endpoint(cdev, usb9pfs, usb9pfs->out_ep);
>>+ if (result)
>>+ goto disable_in;
>>+
>>+ result = alloc_requests(cdev, usb9pfs);
>>+ if (result)
>>+ goto disable_out;
>>+
>>+ dev_dbg(&cdev->gadget->dev, "%s enabled\n", usb9pfs->function.name);
>>+ return 0;
>>+
>>+disable_out:
>>+ usb_ep_disable(usb9pfs->out_ep);
>>+disable_in:
>>+ usb_ep_disable(usb9pfs->in_ep);
>>+out:
>>+ return result;
>>+}
>>+
>>+static int p9_usbg_create(struct p9_client *client, const char *devname, char *args)
>>+{
>>+ struct usb_composite_dev *cdev;
>>+ struct f_usb9pfs *usb9pfs;
>>+ struct f_usb9pfs *tmp;
>>+ struct usb_function *f;
>>+ int ret = -ENOENT;
>>+ int found = 0;
>>+
>>+ if (!devname)
>>+ return -EINVAL;
>>+
>>+ mutex_lock(&usb9pfs_lock);
>>+ list_for_each_entry_safe(usb9pfs, tmp, &usbg_function_list, function_list) {
>>+ if (!usb9pfs->tag)
>>+ continue;
>>+ if (!strncmp(devname, usb9pfs->tag, strlen(devname))) {
>>+ if (!usb9pfs->inuse) {
>>+ usb9pfs->inuse = true;
>>+ found = 1;
>>+ break;
>>+ }
>>+ ret = -EBUSY;
>>+ break;
>>+ }
>>+ }
>>+ mutex_unlock(&usb9pfs_lock);
>>+
>>+ if (!found) {
>>+ pr_err("no channels available for device %s\n", devname);
>>+ return ret;
>>+ }
>>+
>>+ INIT_LIST_HEAD(&usb9pfs->tx_req_list);
>>+
>>+ spin_lock_init(&usb9pfs->lock);
>>+ spin_lock_init(&usb9pfs->req_lock);
>>+
>>+ f = &usb9pfs->function;
>>+ cdev = f->config->cdev;
>>+
>>+ client->trans = (void *)usb9pfs;
>>+ client->status = Connected;
>>+ usb9pfs->client = client;
>>+
>>+ client->trans_mod->maxsize = usb9pfs->buflen;
>>+
>>+ disable_usb9pfs(usb9pfs);
>>+
>>+ return enable_usb9pfs(cdev, usb9pfs);
>
>This looks a bit weird. Clearly some side effect is intended here.
>Can you document here, why and what is expected?
This is probably due to some copy paste left over. I removed the extra
disable path.
>>+}
>>+
>>+static void p9_usbg_close(struct p9_client *client)
>>+{
>>+ struct f_usb9pfs *usb9pfs = client->trans;
>>+
>>+ disable_usb9pfs(usb9pfs);
>>+}
>>+
>>+static int p9_usbg_request(struct p9_client *client, struct p9_req_t *p9_req)
>>+{
>>+ struct f_usb9pfs *usb9pfs = client->trans;
>>+ unsigned long flags;
>>+
>>+ spin_lock_irqsave(&usb9pfs->lock, flags);
>>+ list_add_tail(&p9_req->req_list, &usb9pfs->tx_req_list);
>>+ spin_unlock_irqrestore(&usb9pfs->lock, flags);
>>+
>>+ spin_lock_irqsave(&usb9pfs->req_lock, flags);
>>+ usb9pfs_transmit(usb9pfs);
>>+ spin_unlock_irqrestore(&usb9pfs->req_lock, flags);
>>+
>>+ return 0;
>>+}
>>+
>>+/* We don't currently allow canceling of requests */
>
>What would we gain by allowing those? In other words,
>what are we losing?
As suggested by Dominique I added the cancel callback.
>Regards,
>
>Andrzej
>
>>+static int p9_usbg_cancel(struct p9_client *client, struct p9_req_t *req)
>>+{
>>+ return 1;
>>+}
>>+
>>+static struct p9_trans_module p9_usbg_trans = {
>>+ .name = "usbg",
>>+ .create = p9_usbg_create,
>>+ .close = p9_usbg_close,
>>+ .request = p9_usbg_request,
>>+ .cancel = p9_usbg_cancel,
>>+ .owner = THIS_MODULE,
>>+};
>>+
>>+/*-------------------------------------------------------------------------*/
>>+
>>+#define USB_PROTOCOL_9PFS 0x09
>>+
>>+static struct usb_interface_descriptor usb9pfs_intf = {
>>+ .bLength = sizeof(usb9pfs_intf),
>>+ .bDescriptorType = USB_DT_INTERFACE,
>>+
>>+ .bNumEndpoints = 2,
>>+ .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
>>+ .bInterfaceSubClass = USB_SUBCLASS_VENDOR_SPEC,
>>+ .bInterfaceProtocol = USB_PROTOCOL_9PFS,
>>+
>>+ /* .iInterface = DYNAMIC */
>>+};
>>+
>>+/* full speed support: */
>>+
>>+static struct usb_endpoint_descriptor fs_usb9pfs_source_desc = {
>>+ .bLength = USB_DT_ENDPOINT_SIZE,
>>+ .bDescriptorType = USB_DT_ENDPOINT,
>>+
>>+ .bEndpointAddress = USB_DIR_IN,
>>+ .bmAttributes = USB_ENDPOINT_XFER_BULK,
>>+};
>>+
>>+static struct usb_endpoint_descriptor fs_usb9pfs_sink_desc = {
>>+ .bLength = USB_DT_ENDPOINT_SIZE,
>>+ .bDescriptorType = USB_DT_ENDPOINT,
>>+
>>+ .bEndpointAddress = USB_DIR_OUT,
>>+ .bmAttributes = USB_ENDPOINT_XFER_BULK,
>>+};
>>+
>>+static struct usb_descriptor_header *fs_usb9pfs_descs[] = {
>>+ (struct usb_descriptor_header *)&usb9pfs_intf,
>>+ (struct usb_descriptor_header *)&fs_usb9pfs_sink_desc,
>>+ (struct usb_descriptor_header *)&fs_usb9pfs_source_desc,
>>+ NULL,
>>+};
>>+
>>+/* high speed support: */
>>+
>>+static struct usb_endpoint_descriptor hs_usb9pfs_source_desc = {
>>+ .bLength = USB_DT_ENDPOINT_SIZE,
>>+ .bDescriptorType = USB_DT_ENDPOINT,
>>+
>>+ .bmAttributes = USB_ENDPOINT_XFER_BULK,
>>+ .wMaxPacketSize = cpu_to_le16(512),
>>+};
>>+
>>+static struct usb_endpoint_descriptor hs_usb9pfs_sink_desc = {
>>+ .bLength = USB_DT_ENDPOINT_SIZE,
>>+ .bDescriptorType = USB_DT_ENDPOINT,
>>+
>>+ .bmAttributes = USB_ENDPOINT_XFER_BULK,
>>+ .wMaxPacketSize = cpu_to_le16(512),
>>+};
>>+
>>+static struct usb_descriptor_header *hs_usb9pfs_descs[] = {
>>+ (struct usb_descriptor_header *)&usb9pfs_intf,
>>+ (struct usb_descriptor_header *)&hs_usb9pfs_source_desc,
>>+ (struct usb_descriptor_header *)&hs_usb9pfs_sink_desc,
>>+ NULL,
>>+};
>>+
>>+/* super speed support: */
>>+
>>+static struct usb_endpoint_descriptor ss_usb9pfs_source_desc = {
>>+ .bLength = USB_DT_ENDPOINT_SIZE,
>>+ .bDescriptorType = USB_DT_ENDPOINT,
>>+
>>+ .bmAttributes = USB_ENDPOINT_XFER_BULK,
>>+ .wMaxPacketSize = cpu_to_le16(1024),
>>+};
>>+
>>+static struct usb_ss_ep_comp_descriptor ss_usb9pfs_source_comp_desc = {
>>+ .bLength = USB_DT_SS_EP_COMP_SIZE,
>>+ .bDescriptorType = USB_DT_SS_ENDPOINT_COMP,
>>+ .bMaxBurst = 0,
>>+ .bmAttributes = 0,
>>+ .wBytesPerInterval = 0,
>>+};
>>+
>>+static struct usb_endpoint_descriptor ss_usb9pfs_sink_desc = {
>>+ .bLength = USB_DT_ENDPOINT_SIZE,
>>+ .bDescriptorType = USB_DT_ENDPOINT,
>>+
>>+ .bmAttributes = USB_ENDPOINT_XFER_BULK,
>>+ .wMaxPacketSize = cpu_to_le16(1024),
>>+};
>>+
>>+static struct usb_ss_ep_comp_descriptor ss_usb9pfs_sink_comp_desc = {
>>+ .bLength = USB_DT_SS_EP_COMP_SIZE,
>>+ .bDescriptorType = USB_DT_SS_ENDPOINT_COMP,
>>+ .bMaxBurst = 0,
>>+ .bmAttributes = 0,
>>+ .wBytesPerInterval = 0,
>>+};
>>+
>>+static struct usb_descriptor_header *ss_usb9pfs_descs[] = {
>>+ (struct usb_descriptor_header *)&usb9pfs_intf,
>>+ (struct usb_descriptor_header *)&ss_usb9pfs_source_desc,
>>+ (struct usb_descriptor_header *)&ss_usb9pfs_source_comp_desc,
>>+ (struct usb_descriptor_header *)&ss_usb9pfs_sink_desc,
>>+ (struct usb_descriptor_header *)&ss_usb9pfs_sink_comp_desc,
>>+ NULL,
>>+};
>>+
>>+/* function-specific strings: */
>>+static struct usb_string strings_usb9pfs[] = {
>>+ [0].s = "usb9pfs input to output",
>>+ { } /* end of list */
>>+};
>>+
>>+static struct usb_gadget_strings stringtab_usb9pfs = {
>>+ .language = 0x0409, /* en-us */
>>+ .strings = strings_usb9pfs,
>>+};
>>+
>>+static struct usb_gadget_strings *usb9pfs_strings[] = {
>>+ &stringtab_usb9pfs,
>>+ NULL,
>>+};
>>+
>>+/*-------------------------------------------------------------------------*/
>>+
>>+static int usb9pfs_func_bind(struct usb_configuration *c,
>>+ struct usb_function *f)
>>+{
>>+ struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
>>+ struct usb_composite_dev *cdev = c->cdev;
>>+ int ret;
>>+ int id;
>>+
>>+ /* allocate interface ID(s) */
>>+ id = usb_interface_id(c, f);
>>+ if (id < 0)
>>+ return id;
>>+ usb9pfs_intf.bInterfaceNumber = id;
>>+
>>+ id = usb_string_id(cdev);
>>+ if (id < 0)
>>+ return id;
>>+ strings_usb9pfs[0].id = id;
>>+ usb9pfs_intf.iInterface = id;
>>+
>>+ /* allocate endpoints */
>>+ usb9pfs->in_ep = usb_ep_autoconfig(cdev->gadget,
>>+ &fs_usb9pfs_source_desc);
>>+ if (!usb9pfs->in_ep)
>>+ goto autoconf_fail;
>>+
>>+ usb9pfs->out_ep = usb_ep_autoconfig(cdev->gadget,
>>+ &fs_usb9pfs_sink_desc);
>>+ if (!usb9pfs->out_ep)
>>+ goto autoconf_fail;
>>+
>>+ /* support high speed hardware */
>>+ hs_usb9pfs_source_desc.bEndpointAddress =
>>+ fs_usb9pfs_source_desc.bEndpointAddress;
>>+ hs_usb9pfs_sink_desc.bEndpointAddress = fs_usb9pfs_sink_desc.bEndpointAddress;
>>+
>>+ /* support super speed hardware */
>>+ ss_usb9pfs_source_desc.bEndpointAddress =
>>+ fs_usb9pfs_source_desc.bEndpointAddress;
>>+ ss_usb9pfs_sink_desc.bEndpointAddress = fs_usb9pfs_sink_desc.bEndpointAddress;
>>+
>>+ ret = usb_assign_descriptors(f, fs_usb9pfs_descs, hs_usb9pfs_descs,
>>+ ss_usb9pfs_descs, ss_usb9pfs_descs);
>>+ if (ret)
>>+ return ret;
>>+
>>+ dev_dbg(&cdev->gadget->dev, "%s speed %s: IN/%s, OUT/%s\n",
>>+ (gadget_is_superspeed(c->cdev->gadget) ? "super" :
>>+ (gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full")),
>>+ f->name, usb9pfs->in_ep->name, usb9pfs->out_ep->name);
>>+ return 0;
>>+
>>+autoconf_fail:
>>+ ERROR(cdev, "%s: can't autoconfigure on %s\n",
>>+ f->name, cdev->gadget->name);
>>+ return -ENODEV;
>>+}
>>+
>>+static void usb9pfs_free_func(struct usb_function *f)
>>+{
>>+ struct f_usb9pfs *usb9pfs = func_to_usb9pfs(f);
>>+ struct f_usb9pfs_opts *opts;
>>+
>>+ ida_free(&usb9pfs_ida, usb9pfs->index);
>>+ kfree(usb9pfs->tag);
>>+ kfree(usb9pfs);
>>+
>>+ opts = container_of(f->fi, struct f_usb9pfs_opts, func_inst);
>>+
>>+ mutex_lock(&opts->lock);
>>+ opts->refcnt--;
>>+ mutex_unlock(&opts->lock);
>>+
>>+ usb_free_all_descriptors(f);
>>+}
>>+
>>+static int usb9pfs_set_alt(struct usb_function *f,
>>+ unsigned int intf, unsigned int alt)
>>+{
>>+ return 0;
>>+}
>>+
>>+static void usb9pfs_disable(struct usb_function *f)
>>+{
>>+}
>>+
>>+static struct usb_function *usb9pfs_alloc(struct usb_function_instance *fi)
>>+{
>>+ struct f_usb9pfs_opts *usb9pfs_opts;
>>+ struct f_usb9pfs *usb9pfs;
>>+
>>+ usb9pfs = kzalloc(sizeof(*usb9pfs), GFP_KERNEL);
>>+ if (!usb9pfs)
>>+ return ERR_PTR(-ENOMEM);
>>+
>>+ usb9pfs_opts = container_of(fi, struct f_usb9pfs_opts, func_inst);
>>+
>>+ mutex_lock(&usb9pfs_opts->lock);
>>+ usb9pfs_opts->refcnt++;
>>+ mutex_unlock(&usb9pfs_opts->lock);
>>+
>>+ usb9pfs->buflen = usb9pfs_opts->buflen;
>>+
>>+ usb9pfs->function.name = "usb9pfs";
>>+ usb9pfs->function.bind = usb9pfs_func_bind;
>>+ usb9pfs->function.set_alt = usb9pfs_set_alt;
>>+ usb9pfs->function.disable = usb9pfs_disable;
>>+ usb9pfs->function.strings = usb9pfs_strings;
>>+
>>+ usb9pfs->function.free_func = usb9pfs_free_func;
>>+
>>+ mutex_lock(&usb9pfs_ida_lock);
>>+
>>+ usb9pfs->index = ida_alloc_max(&usb9pfs_ida, U8_MAX, GFP_KERNEL);
>>+ if (usb9pfs->index < 0) {
>>+ struct usb_function *ret = ERR_PTR(usb9pfs->index);
>>+
>>+ kfree(usb9pfs);
>>+ mutex_unlock(&usb9pfs_ida_lock);
>>+ return ret;
>>+ }
>>+
>>+ mutex_unlock(&usb9pfs_ida_lock);
>>+
>>+ usb9pfs->tag = kasprintf(GFP_KERNEL, "%s%d", usb9pfs->function.name,
>>+ usb9pfs->index);
>>+
>>+ INIT_LIST_HEAD(&usb9pfs->function_list);
>>+
>>+ mutex_lock(&usb9pfs_lock);
>>+ list_add_tail(&usb9pfs->function_list, &usbg_function_list);
>>+ mutex_unlock(&usb9pfs_lock);
>>+
>>+ return &usb9pfs->function;
>>+}
>>+
>>+static inline struct f_usb9pfs_opts *to_f_usb9pfs_opts(struct config_item *item)
>>+{
>>+ return container_of(to_config_group(item), struct f_usb9pfs_opts,
>>+ func_inst.group);
>>+}
>>+
>>+static void usb9pfs_attr_release(struct config_item *item)
>>+{
>>+ struct f_usb9pfs_opts *usb9pfs_opts = to_f_usb9pfs_opts(item);
>>+
>>+ usb_put_function_instance(&usb9pfs_opts->func_inst);
>>+}
>>+
>>+static struct configfs_item_operations usb9pfs_item_ops = {
>>+ .release = usb9pfs_attr_release,
>>+};
>>+
>>+static ssize_t f_usb9pfs_opts_buflen_show(struct config_item *item, char *page)
>>+{
>>+ struct f_usb9pfs_opts *opts = to_f_usb9pfs_opts(item);
>>+ int result;
>>+
>>+ mutex_lock(&opts->lock);
>>+ result = sprintf(page, "%d\n", opts->buflen);
>>+ mutex_unlock(&opts->lock);
>>+
>>+ return result;
>>+}
>>+
>>+static ssize_t f_usb9pfs_opts_buflen_store(struct config_item *item,
>>+ const char *page, size_t len)
>>+{
>>+ struct f_usb9pfs_opts *opts = to_f_usb9pfs_opts(item);
>>+ int ret;
>>+ u32 num;
>>+
>>+ mutex_lock(&opts->lock);
>>+ if (opts->refcnt) {
>>+ ret = -EBUSY;
>>+ goto end;
>>+ }
>>+
>>+ ret = kstrtou32(page, 0, &num);
>>+ if (ret)
>>+ goto end;
>>+
>>+ opts->buflen = num;
>>+ ret = len;
>>+end:
>>+ mutex_unlock(&opts->lock);
>>+ return ret;
>>+}
>>+
>>+CONFIGFS_ATTR(f_usb9pfs_opts_, buflen);
>>+
>>+static struct configfs_attribute *usb9pfs_attrs[] = {
>>+ &f_usb9pfs_opts_attr_buflen,
>>+ NULL,
>>+};
>>+
>>+static const struct config_item_type usb9pfs_func_type = {
>>+ .ct_item_ops = &usb9pfs_item_ops,
>>+ .ct_attrs = usb9pfs_attrs,
>>+ .ct_owner = THIS_MODULE,
>>+};
>>+
>>+static void usb9pfs_free_instance(struct usb_function_instance *fi)
>>+{
>>+ struct f_usb9pfs_opts *usb9pfs_opts;
>>+
>>+ usb9pfs_opts = container_of(fi, struct f_usb9pfs_opts, func_inst);
>>+ kfree(usb9pfs_opts);
>>+}
>>+
>>+static struct usb_function_instance *usb9pfs_alloc_instance(void)
>>+{
>>+ struct f_usb9pfs_opts *usb9pfs_opts;
>>+
>>+ usb9pfs_opts = kzalloc(sizeof(*usb9pfs_opts), GFP_KERNEL);
>>+ if (!usb9pfs_opts)
>>+ return ERR_PTR(-ENOMEM);
>>+
>>+ mutex_init(&usb9pfs_opts->lock);
>>+
>>+ usb9pfs_opts->func_inst.free_func_inst = usb9pfs_free_instance;
>>+
>>+ usb9pfs_opts->buflen = DEFAULT_BUFLEN;
>>+
>>+ config_group_init_type_name(&usb9pfs_opts->func_inst.group, "",
>>+ &usb9pfs_func_type);
>>+
>>+ return &usb9pfs_opts->func_inst;
>>+}
>>+DECLARE_USB_FUNCTION(usb9pfs, usb9pfs_alloc_instance, usb9pfs_alloc);
>>+
>>+static int __init usb9pfs_modinit(void)
>>+{
>>+ int ret;
>>+
>>+ INIT_LIST_HEAD(&usbg_function_list);
>>+
>>+ ret = usb_function_register(&usb9pfsusb_func);
>>+ if (!ret)
>>+ v9fs_register_trans(&p9_usbg_trans);
>>+
>>+ return ret;
>>+}
>>+
>>+static void __exit usb9pfs_modexit(void)
>>+{
>>+ usb_function_unregister(&usb9pfsusb_func);
>>+ v9fs_unregister_trans(&p9_usbg_trans);
>>+}
>>+
>>+module_init(usb9pfs_modinit);
>>+module_exit(usb9pfs_modexit);
>>+
>>+MODULE_ALIAS_9P("usbg");
>>+MODULE_LICENSE("GPL");
>>+MODULE_DESCRIPTION("USB gadget 9pfs transport");
>>+MODULE_AUTHOR("Michael Grzeschik");
>>
>
>
>
--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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