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Message-ID: <CANP3RGffmZi+dJy1GWf7CnnA189RFNwg1ScsTve_6HniJOkydw@mail.gmail.com>
Date: Mon, 23 Aug 2021 19:50:08 +0200
From: Maciej Żenczykowski <maze@...gle.com>
To: Maxim Devaev <mdevaev@...il.com>
Cc: balbi@...nel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
ruslan.bilovol@...il.com, mika.westerberg@...ux.intel.com,
jj251510319013@...il.com, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] usb: gadget: f_hid: optional SETUP/SET_REPORT mode
On Sat, Aug 21, 2021 at 3:40 PM Maxim Devaev <mdevaev@...il.com> wrote:
>
> f_hid provides the OUT Endpoint as only way for receiving reports
> from the host. SETUP/SET_REPORT method is not supported, and this causes
> a number of compatibility problems with various host drivers, especially
> in the case of keyboard emulation using f_hid.
>
> - Some hosts do not support the OUT Endpoint and ignore it,
> so it becomes impossible for the gadget to receive a report
> from the host. In the case of a keyboard, the gadget loses
> the ability to receive the status of the LEDs.
>
> - Some BIOSes/UEFIs can't work with HID devices with the OUT Endpoint
> at all. This may be due to their bugs or incomplete implementation
> of the HID standard.
> For example, absolutely all Apple UEFIs can't handle the OUT Endpoint
> if it goes after IN Endpoint in the descriptor and require the reverse
> order (OUT, IN) which is a violation of the standard.
> Other hosts either do not initialize gadgets with a descriptor
> containing the OUT Endpoint completely (like some HP and DELL BIOSes
> and embedded firmwares like on KVM switches), or initialize them,
> but will not poll the IN Endpoint.
>
> This patch adds configfs option no_out_endpoint=1 to disable
> the OUT Endpoint and allows f_hid to receive reports from the host
> via SETUP/SET_REPORT.
>
> Previously, there was such a feature in f_hid, but it was replaced
> by the OUT Endpoint [1] in the commit 99c515005857 ("usb: gadget: hidg:
> register OUT INT endpoint for SET_REPORT"). So this patch actually
> returns the removed functionality while making it optional.
> For backward compatibility reasons, the OUT Endpoint mode remains
> the default behaviour.
>
> - The OUT Endpoint mode provides the report queue and reduces
> USB overhead (eliminating SETUP routine) on transmitting a report
> from the host.
>
> - If the SETUP/SET_REPORT mode is used, there is no report queue,
> so the userspace will only read last report. For classic HID devices
> like keyboards this is not a problem, since it's intended to transmit
> the status of the LEDs and only the last report is important.
> This mode provides better compatibility with strange and buggy
> host drivers.
>
> Both modes passed USBCV tests. Checking with the USB protocol analyzer
> also confirmed that everything is working as it should and the new mode
> ensures operability in all of the described cases.
>
> Signed-off-by: Maxim Devaev <mdevaev@...il.com>
> Link: https://www.spinics.net/lists/linux-usb/msg65494.html [1]
> ---
> drivers/usb/gadget/function/f_hid.c | 220 +++++++++++++++++++++++-----
> drivers/usb/gadget/function/u_hid.h | 1 +
> 2 files changed, 188 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
> index bb476e121eae..ca0a7d9eaa34 100644
> --- a/drivers/usb/gadget/function/f_hid.c
> +++ b/drivers/usb/gadget/function/f_hid.c
> @@ -45,12 +45,25 @@ struct f_hidg {
> unsigned short report_desc_length;
> char *report_desc;
> unsigned short report_length;
> + /*
> + * use_out_ep - if true, the OUT Endpoint (interrupt out method)
> + * will be used to receive reports from the host
> + * using functions with the "intout" suffix.
> + * Otherwise, the OUT Endpoint will not be configured
> + * and the SETUP/SET_REPORT method ("ssreport" suffix)
> + * will be used to receive reports.
> + */
> + bool use_out_ep;
>
> /* recv report */
> - struct list_head completed_out_req;
> spinlock_t read_spinlock;
> wait_queue_head_t read_queue;
> + /* recv report - interrupt out only (use_out_ep == 1) */
> + struct list_head completed_out_req;
> unsigned int qlen;
> + /* recv report - setup set_report only (use_out_ep == 0) */
> + char *set_report_buf;
> + unsigned int set_report_length;
>
> /* send report */
> spinlock_t write_spinlock;
> @@ -79,7 +92,7 @@ static struct usb_interface_descriptor hidg_interface_desc = {
> .bDescriptorType = USB_DT_INTERFACE,
> /* .bInterfaceNumber = DYNAMIC */
> .bAlternateSetting = 0,
> - .bNumEndpoints = 2,
> + /* .bNumEndpoints = DYNAMIC (depends on use_out_ep) */
> .bInterfaceClass = USB_CLASS_HID,
> /* .bInterfaceSubClass = DYNAMIC */
> /* .bInterfaceProtocol = DYNAMIC */
> @@ -140,7 +153,7 @@ static struct usb_ss_ep_comp_descriptor hidg_ss_out_comp_desc = {
> /* .wBytesPerInterval = DYNAMIC */
> };
>
> -static struct usb_descriptor_header *hidg_ss_descriptors[] = {
> +static struct usb_descriptor_header *hidg_ss_descriptors_intout[] = {
> (struct usb_descriptor_header *)&hidg_interface_desc,
> (struct usb_descriptor_header *)&hidg_desc,
> (struct usb_descriptor_header *)&hidg_ss_in_ep_desc,
> @@ -150,6 +163,14 @@ static struct usb_descriptor_header *hidg_ss_descriptors[] = {
> NULL,
> };
>
> +static struct usb_descriptor_header *hidg_ss_descriptors_ssreport[] = {
> + (struct usb_descriptor_header *)&hidg_interface_desc,
> + (struct usb_descriptor_header *)&hidg_desc,
> + (struct usb_descriptor_header *)&hidg_ss_in_ep_desc,
> + (struct usb_descriptor_header *)&hidg_ss_in_comp_desc,
> + NULL,
> +};
> +
> /* High-Speed Support */
>
> static struct usb_endpoint_descriptor hidg_hs_in_ep_desc = {
> @@ -176,7 +197,7 @@ static struct usb_endpoint_descriptor hidg_hs_out_ep_desc = {
> */
> };
>
> -static struct usb_descriptor_header *hidg_hs_descriptors[] = {
> +static struct usb_descriptor_header *hidg_hs_descriptors_intout[] = {
> (struct usb_descriptor_header *)&hidg_interface_desc,
> (struct usb_descriptor_header *)&hidg_desc,
> (struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
> @@ -184,6 +205,13 @@ static struct usb_descriptor_header *hidg_hs_descriptors[] = {
> NULL,
> };
>
> +static struct usb_descriptor_header *hidg_hs_descriptors_ssreport[] = {
> + (struct usb_descriptor_header *)&hidg_interface_desc,
> + (struct usb_descriptor_header *)&hidg_desc,
> + (struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
> + NULL,
> +};
> +
> /* Full-Speed Support */
>
> static struct usb_endpoint_descriptor hidg_fs_in_ep_desc = {
> @@ -210,7 +238,7 @@ static struct usb_endpoint_descriptor hidg_fs_out_ep_desc = {
> */
> };
>
> -static struct usb_descriptor_header *hidg_fs_descriptors[] = {
> +static struct usb_descriptor_header *hidg_fs_descriptors_intout[] = {
> (struct usb_descriptor_header *)&hidg_interface_desc,
> (struct usb_descriptor_header *)&hidg_desc,
> (struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
> @@ -218,6 +246,13 @@ static struct usb_descriptor_header *hidg_fs_descriptors[] = {
> NULL,
> };
>
> +static struct usb_descriptor_header *hidg_fs_descriptors_ssreport[] = {
> + (struct usb_descriptor_header *)&hidg_interface_desc,
> + (struct usb_descriptor_header *)&hidg_desc,
> + (struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
> + NULL,
> +};
> +
> /*-------------------------------------------------------------------------*/
> /* Strings */
>
> @@ -241,8 +276,8 @@ static struct usb_gadget_strings *ct_func_strings[] = {
> /*-------------------------------------------------------------------------*/
> /* Char Device */
>
> -static ssize_t f_hidg_read(struct file *file, char __user *buffer,
> - size_t count, loff_t *ptr)
> +static ssize_t f_hidg_intout_read(struct file *file, char __user *buffer,
> + size_t count, loff_t *ptr)
> {
> struct f_hidg *hidg = file->private_data;
> struct f_hidg_req_list *list;
> @@ -255,15 +290,15 @@ static ssize_t f_hidg_read(struct file *file, char __user *buffer,
>
> spin_lock_irqsave(&hidg->read_spinlock, flags);
>
> -#define READ_COND (!list_empty(&hidg->completed_out_req))
> +#define READ_COND_INTOUT (!list_empty(&hidg->completed_out_req))
>
> /* wait for at least one buffer to complete */
> - while (!READ_COND) {
> + while (!READ_COND_INTOUT) {
> spin_unlock_irqrestore(&hidg->read_spinlock, flags);
> if (file->f_flags & O_NONBLOCK)
> return -EAGAIN;
>
> - if (wait_event_interruptible(hidg->read_queue, READ_COND))
> + if (wait_event_interruptible(hidg->read_queue, READ_COND_INTOUT))
> return -ERESTARTSYS;
>
> spin_lock_irqsave(&hidg->read_spinlock, flags);
> @@ -313,6 +348,60 @@ static ssize_t f_hidg_read(struct file *file, char __user *buffer,
> return count;
> }
>
> +#define READ_COND_SSREPORT (hidg->set_report_buf != NULL)
> +
> +static ssize_t f_hidg_ssreport_read(struct file *file, char __user *buffer,
> + size_t count, loff_t *ptr)
> +{
> + struct f_hidg *hidg = file->private_data;
> + char *tmp_buf = NULL;
> + unsigned long flags;
> +
> + if (!count)
> + return 0;
> +
> + spin_lock_irqsave(&hidg->read_spinlock, flags);
> +
> + while (!READ_COND_SSREPORT) {
> + spin_unlock_irqrestore(&hidg->read_spinlock, flags);
> + if (file->f_flags & O_NONBLOCK)
> + return -EAGAIN;
> +
> + if (wait_event_interruptible(hidg->read_queue, READ_COND_SSREPORT))
> + return -ERESTARTSYS;
> +
> + spin_lock_irqsave(&hidg->read_spinlock, flags);
> + }
> +
> + count = min_t(unsigned int, count, hidg->set_report_length);
> + tmp_buf = hidg->set_report_buf;
> + hidg->set_report_buf = NULL;
> +
> + spin_unlock_irqrestore(&hidg->read_spinlock, flags);
> +
> + if (tmp_buf != NULL) {
> + count -= copy_to_user(buffer, tmp_buf, count);
> + kfree(tmp_buf);
> + } else {
> + count = -ENOMEM;
> + }
> +
> + wake_up(&hidg->read_queue);
> +
> + return count;
> +}
> +
> +static ssize_t f_hidg_read(struct file *file, char __user *buffer,
> + size_t count, loff_t *ptr)
> +{
> + struct f_hidg *hidg = file->private_data;
> +
> + if (hidg->use_out_ep)
> + return f_hidg_intout_read(file, buffer, count, ptr);
> + else
> + return f_hidg_ssreport_read(file, buffer, count, ptr);
> +}
> +
> static void f_hidg_req_complete(struct usb_ep *ep, struct usb_request *req)
> {
> struct f_hidg *hidg = (struct f_hidg *)ep->driver_data;
> @@ -433,14 +522,20 @@ static __poll_t f_hidg_poll(struct file *file, poll_table *wait)
> if (WRITE_COND)
> ret |= EPOLLOUT | EPOLLWRNORM;
>
> - if (READ_COND)
> - ret |= EPOLLIN | EPOLLRDNORM;
> + if (hidg->use_out_ep) {
> + if (READ_COND_INTOUT)
> + ret |= EPOLLIN | EPOLLRDNORM;
> + } else {
> + if (READ_COND_SSREPORT)
> + ret |= EPOLLIN | EPOLLRDNORM;
> + }
>
> return ret;
> }
>
> #undef WRITE_COND
> -#undef READ_COND
> +#undef READ_COND_SSREPORT
> +#undef READ_COND_INTOUT
>
> static int f_hidg_release(struct inode *inode, struct file *fd)
> {
> @@ -467,7 +562,7 @@ static inline struct usb_request *hidg_alloc_ep_req(struct usb_ep *ep,
> return alloc_ep_req(ep, length);
> }
>
> -static void hidg_set_report_complete(struct usb_ep *ep, struct usb_request *req)
> +static void hidg_intout_complete(struct usb_ep *ep, struct usb_request *req)
> {
> struct f_hidg *hidg = (struct f_hidg *) req->context;
> struct usb_composite_dev *cdev = hidg->func.config->cdev;
> @@ -502,6 +597,37 @@ static void hidg_set_report_complete(struct usb_ep *ep, struct usb_request *req)
> }
> }
>
> +static void hidg_ssreport_complete(struct usb_ep *ep, struct usb_request *req)
> +{
> + struct f_hidg *hidg = (struct f_hidg *)req->context;
> + struct usb_composite_dev *cdev = hidg->func.config->cdev;
> + char *new_buf = NULL;
> + unsigned long flags;
> +
> + if (req->status != 0 || req->buf == NULL || req->actual == 0) {
> + ERROR(cdev,
> + "%s FAILED: status=%d, buf=%p, actual=%d\n",
> + __func__, req->status, req->buf, req->actual);
> + return;
> + }
> +
> + spin_lock_irqsave(&hidg->read_spinlock, flags);
> +
> + new_buf = krealloc(hidg->set_report_buf, req->actual, GFP_ATOMIC);
> + if (new_buf == NULL) {
> + spin_unlock_irqrestore(&hidg->read_spinlock, flags);
> + return;
> + }
> + hidg->set_report_buf = new_buf;
> +
> + hidg->set_report_length = req->actual;
> + memcpy(hidg->set_report_buf, req->buf, req->actual);
> +
> + spin_unlock_irqrestore(&hidg->read_spinlock, flags);
> +
> + wake_up(&hidg->read_queue);
> +}
> +
> static int hidg_setup(struct usb_function *f,
> const struct usb_ctrlrequest *ctrl)
> {
> @@ -549,7 +675,11 @@ static int hidg_setup(struct usb_function *f,
> case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
> | HID_REQ_SET_REPORT):
> VDBG(cdev, "set_report | wLength=%d\n", ctrl->wLength);
> - goto stall;
> + if (hidg->use_out_ep)
> + goto stall;
> + req->complete = hidg_ssreport_complete;
> + req->context = hidg;
> + goto respond;
> break;
>
> case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
> @@ -637,15 +767,18 @@ static void hidg_disable(struct usb_function *f)
> unsigned long flags;
>
> usb_ep_disable(hidg->in_ep);
> - usb_ep_disable(hidg->out_ep);
>
> - spin_lock_irqsave(&hidg->read_spinlock, flags);
> - list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
> - free_ep_req(hidg->out_ep, list->req);
> - list_del(&list->list);
> - kfree(list);
> + if (hidg->out_ep) {
> + usb_ep_disable(hidg->out_ep);
> +
> + spin_lock_irqsave(&hidg->read_spinlock, flags);
> + list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
> + free_ep_req(hidg->out_ep, list->req);
> + list_del(&list->list);
> + kfree(list);
> + }
> + spin_unlock_irqrestore(&hidg->read_spinlock, flags);
> }
> - spin_unlock_irqrestore(&hidg->read_spinlock, flags);
>
> spin_lock_irqsave(&hidg->write_spinlock, flags);
> if (!hidg->write_pending) {
> @@ -691,8 +824,7 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
> }
> }
>
> -
> - if (hidg->out_ep != NULL) {
> + if (hidg->use_out_ep && hidg->out_ep != NULL) {
> /* restart endpoint */
> usb_ep_disable(hidg->out_ep);
>
> @@ -717,7 +849,7 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
> hidg_alloc_ep_req(hidg->out_ep,
> hidg->report_length);
> if (req) {
> - req->complete = hidg_set_report_complete;
> + req->complete = hidg_intout_complete;
> req->context = hidg;
> status = usb_ep_queue(hidg->out_ep, req,
> GFP_ATOMIC);
> @@ -743,7 +875,8 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
> }
> return 0;
> disable_out_ep:
> - usb_ep_disable(hidg->out_ep);
> + if (hidg->out_ep)
> + usb_ep_disable(hidg->out_ep);
> free_req_in:
> if (req_in)
> free_ep_req(hidg->in_ep, req_in);
> @@ -795,14 +928,21 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
> goto fail;
> hidg->in_ep = ep;
>
> - ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_out_ep_desc);
> - if (!ep)
> - goto fail;
> - hidg->out_ep = ep;
> + hidg->out_ep = NULL;
> + if (hidg->use_out_ep) {
> + ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_out_ep_desc);
> + if (!ep)
> + goto fail;
> + hidg->out_ep = ep;
> + }
> +
> + /* used only if use_out_ep == 1 */
> + hidg->set_report_buf = NULL;
>
> /* set descriptor dynamic values */
> hidg_interface_desc.bInterfaceSubClass = hidg->bInterfaceSubClass;
> hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
> + hidg_interface_desc.bNumEndpoints = hidg->use_out_ep ? 2 : 1;
> hidg->protocol = HID_REPORT_PROTOCOL;
> hidg->idle = 1;
> hidg_ss_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
> @@ -833,9 +973,19 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
> hidg_ss_out_ep_desc.bEndpointAddress =
> hidg_fs_out_ep_desc.bEndpointAddress;
>
> - status = usb_assign_descriptors(f, hidg_fs_descriptors,
> - hidg_hs_descriptors, hidg_ss_descriptors,
> - hidg_ss_descriptors);
> + if (hidg->use_out_ep)
> + status = usb_assign_descriptors(f,
> + hidg_fs_descriptors_intout,
> + hidg_hs_descriptors_intout,
> + hidg_ss_descriptors_intout,
> + hidg_ss_descriptors_intout);
> + else
> + status = usb_assign_descriptors(f,
> + hidg_fs_descriptors_ssreport,
> + hidg_hs_descriptors_ssreport,
> + hidg_ss_descriptors_ssreport,
> + hidg_ss_descriptors_ssreport);
> +
> if (status)
> goto fail;
>
> @@ -950,6 +1100,7 @@ CONFIGFS_ATTR(f_hid_opts_, name)
>
> F_HID_OPT(subclass, 8, 255);
> F_HID_OPT(protocol, 8, 255);
> +F_HID_OPT(no_out_endpoint, 8, 1);
> F_HID_OPT(report_length, 16, 65535);
>
> static ssize_t f_hid_opts_report_desc_show(struct config_item *item, char *page)
> @@ -1009,6 +1160,7 @@ CONFIGFS_ATTR_RO(f_hid_opts_, dev);
> static struct configfs_attribute *hid_attrs[] = {
> &f_hid_opts_attr_subclass,
> &f_hid_opts_attr_protocol,
> + &f_hid_opts_attr_no_out_endpoint,
> &f_hid_opts_attr_report_length,
> &f_hid_opts_attr_report_desc,
> &f_hid_opts_attr_dev,
> @@ -1093,6 +1245,7 @@ static void hidg_free(struct usb_function *f)
> hidg = func_to_hidg(f);
> opts = container_of(f->fi, struct f_hid_opts, func_inst);
> kfree(hidg->report_desc);
> + kfree(hidg->set_report_buf);
> kfree(hidg);
> mutex_lock(&opts->lock);
> --opts->refcnt;
> @@ -1139,6 +1292,7 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
> return ERR_PTR(-ENOMEM);
> }
> }
> + hidg->use_out_ep = !opts->no_out_endpoint;
>
> mutex_unlock(&opts->lock);
>
> diff --git a/drivers/usb/gadget/function/u_hid.h b/drivers/usb/gadget/function/u_hid.h
> index 98d6af558c03..84bb70292855 100644
> --- a/drivers/usb/gadget/function/u_hid.h
> +++ b/drivers/usb/gadget/function/u_hid.h
> @@ -20,6 +20,7 @@ struct f_hid_opts {
> int minor;
> unsigned char subclass;
> unsigned char protocol;
> + unsigned char no_out_endpoint;
> unsigned short report_length;
> unsigned short report_desc_length;
> unsigned char *report_desc;
> --
> 2.32.0
Reviewed-by: Maciej Żenczykowski <zenczykowski@...il.com>
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