Date:   Wed, 23 Nov 2022 17:26:42 +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 05:08:10PM CET, mailhol.vincent@...adoo.fr wrote:
>On Wed. 23 Nov. 2022 at 21:10, Jiri Pirko <jiri@...dia.com> wrote:
>> 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?
>
>I mean that device_kind, it does not sound like a field that would
>hold the driver name.
>
>Looking deeper in the code, I got the confirmation.
>bus_info::device_kind is initialized here (among other):
>https://elixir.bootlin.com/linux/v6.1-rc1/source/drivers/net/ethernet/mellanox/mlxsw/i2c.c#L714
>
>and it uses ic2_client::name which indicate the type of the device
>(e.g. chip name):
>https://elixir.bootlin.com/linux/v6.1-rc1/source/include/linux/i2c.h#L317
>
>So I confirm that this is a misuse. This driver does not report the
>driver's name.

Okay, I think that is a bug of mlxsw_i2c implementation. You can fix it
along the way.


>
>> >> >+
>> >> >+      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.
>
>I will do a first patch only for the driver name and think again of
>the USB serial later on.

Yep, thanks!


>
>
>Yours sincerely,
>Vincent Mailhol

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