Date:   Wed, 23 Nov 2022 13:10:26 +0100
From:   Jiri Pirko <jiri@...dia.com>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] net: devlink: devlink_nl_info_fill: populate default
 information

Wed, Nov 23, 2022 at 12:00:44PM CET, mailhol.vincent@...adoo.fr wrote:
>On Wed. 23 nov. 2022 à 18:46, Jiri Pirko <jiri@...dia.com> wrote:
>> Tue, Nov 22, 2022 at 04:49:34PM CET, mailhol.vincent@...adoo.fr wrote:
>> >Some piece of information are common to the vast majority of the
>> >devices. Examples are:
>> >
>> >  * the driver name.
>> >  * the serial number of a USB device.
>> >
>> >Modify devlink_nl_info_fill() to retrieve those information so that
>> >the drivers do not have to. Rationale: factorize code.
>> >
>> >Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
>> >---
>> >I am sending this as an RFC because I just started to study devlink.
>> >
>> >I can see a parallel with ethtool for which the core will fill
>> >whatever it can. c.f.:
>> >commit f20a0a0519f3 ("ethtool: doc: clarify what drivers can implement in their get_drvinfo()")
>> >Link: https://git.kernel.org/netdev/net-next/c/f20a0a0519f3
>> >
>> >I think that devlink should do the same.
>> >
>> >Right now, I identified two fields. If this RFC receive positive
>> >feedback, I will iron it up and try to see if there is more that can
>> >be filled by default.
>> >
>> >Thank you for your comments.
>> >---
>> > net/core/devlink.c | 36 ++++++++++++++++++++++++++++++++++++
>> > 1 file changed, 36 insertions(+)
>> >
>> >diff --git a/net/core/devlink.c b/net/core/devlink.c
>> >index 7f789bbcbbd7..1908b360caf7 100644
>> >--- a/net/core/devlink.c
>> >+++ b/net/core/devlink.c
>> >@@ -18,6 +18,7 @@
>> > #include <linux/netdevice.h>
>> > #include <linux/spinlock.h>
>> > #include <linux/refcount.h>
>> >+#include <linux/usb.h>
>> > #include <linux/workqueue.h>
>> > #include <linux/u64_stats_sync.h>
>> > #include <linux/timekeeping.h>
>> >@@ -6685,12 +6686,37 @@ int devlink_info_version_running_put_ext(struct devlink_info_req *req,
>> > }
>> > EXPORT_SYMBOL_GPL(devlink_info_version_running_put_ext);
>> >
>> >+static int devlink_nl_driver_info_get(struct device_driver *drv,
>> >+                                    struct devlink_info_req *req)
>> >+{
>> >+      if (!drv)
>> >+              return 0;
>> >+
>> >+      if (drv->name[0])
>> >+              return devlink_info_driver_name_put(req, drv->name);
>>
>> Make sure that this provides the same value for all existing drivers
>> using devlink.
>
>There are 21 drivers so far which reports the driver name through devlink. c.f.:
>  $ git grep "devlink_info_driver_name_put(" drivers | wc -l
>
>Out of those 21, there is only one: the mlxsw which seems to report
>something different than device_driver::name. Instead it reports some
>bus_info:
>  https://elixir.bootlin.com/linux/v6.1-rc1/source/drivers/net/ethernet/mellanox/mlxsw/core.c#L1462
>  https://elixir.bootlin.com/linux/v6.1-rc1/source/drivers/net/ethernet/mellanox/mlxsw/core.h#L504
>
>I am not sure what the bus_info is here, but it looks like a misuse of
>the field here.

When you are not sure, look into the code to find out :) I see no misue.
What exactly do you mean by that?


>
>>
>> >+
>> >+      return 0;
>> >+}
>> >+
>> >+static int devlink_nl_usb_info_get(struct usb_device *udev,
>> >+                                 struct devlink_info_req *req)
>> >+{
>> >+      if (!udev)
>> >+              return 0;
>> >+
>> >+      if (udev->serial[0])
>> >+              return devlink_info_serial_number_put(req, udev->serial);
>> >+
>> >+      return 0;
>> >+}
>> >+
>> > static int
>> > devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,
>> >                    enum devlink_command cmd, u32 portid,
>> >                    u32 seq, int flags, struct netlink_ext_ack *extack)
>> > {
>> >       struct devlink_info_req req = {};
>> >+      struct device *dev = devlink_to_dev(devlink);
>> >       void *hdr;
>> >       int err;
>> >
>> >@@ -6707,6 +6733,16 @@ devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,
>> >       if (err)
>> >               goto err_cancel_msg;
>> >
>> >+      err = devlink_nl_driver_info_get(dev->driver, &req);
>> >+      if (err)
>> >+              goto err_cancel_msg;
>> >+
>> >+      if (!strcmp(dev->parent->type->name, "usb_device")) {
>>
>> Comparing to string does not seem correct here.
>
>There is a is_usb_device() which does the check:
>  https://elixir.bootlin.com/linux/v6.1-rc1/source/drivers/usb/core/usb.h#L152
>
>but this macro is not exposed outside of the usb core. The string
>comparison was the only solution I found.

Find a different one. String check here is wrong.


>
>Do you have any other ideas? If not and if this goes further than the
>RFC stage, I will ask the USB folks if there is a better way.
>
>>
>> >+              err = devlink_nl_usb_info_get(to_usb_device(dev->parent), &req);
>>
>> As Jakub pointed out, you have to make sure that driver does not put the
>> same attrs again. You have to introduce this functionality with removing
>> the fill-ups in drivers atomically, in a single patch.
>
>Either this, either track if the attribute is already set. I would
>prefer to remove all drivers fill-ups but this is not feasible for the
>serial number. c.f. my reply to Jacub in this thread:
>  https://lore.kernel.org/netdev/CAMZ6RqJ8_=h1SS7WmBeEB=75wsvVUZrb-8ELCDtpZb0gSs=2+A@mail.gmail.com/

Sure, but for the driver name it is. Let's start there.


>
>> >+              if (err)
>> >+                      goto err_cancel_msg;
>> >+      }
>> >+
>> >       genlmsg_end(msg, hdr);
>> >       return 0;
>> >
>> >--
>> >2.37.4
>> >

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