linux-kernel - Re: [PATCH v6] net: usb: ax88179_178a: avoid failed operations when device is disconnected

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Date:   Thu, 7 Dec 2023 15:23:23 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Jose Ignacio Tornos Martinez <jtornosm@...hat.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, greg@...ah.com,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org,
        oneukum@...e.com, pabeni@...hat.com, stable@...r.kernel.org
Subject: Re: [PATCH v6] net: usb: ax88179_178a: avoid failed operations when
 device is disconnected

On Thu, Dec 07, 2023 at 06:50:07PM +0100, Jose Ignacio Tornos Martinez wrote:
> When the device is disconnected we get the following messages showing
> failed operations:
> Nov 28 20:22:11 localhost kernel: usb 2-3: USB disconnect, device number 2
> Nov 28 20:22:11 localhost kernel: ax88179_178a 2-3:1.0 enp2s0u3: unregister 'ax88179_178a' usb-0000:02:00.0-3, ASIX AX88179 USB 3.0 Gigabit Ethernet
> Nov 28 20:22:11 localhost kernel: ax88179_178a 2-3:1.0 enp2s0u3: Failed to read reg index 0x0002: -19
> Nov 28 20:22:11 localhost kernel: ax88179_178a 2-3:1.0 enp2s0u3: Failed to write reg index 0x0002: -19
> Nov 28 20:22:11 localhost kernel: ax88179_178a 2-3:1.0 enp2s0u3 (unregistered): Failed to write reg index 0x0002: -19
> Nov 28 20:22:11 localhost kernel: ax88179_178a 2-3:1.0 enp2s0u3 (unregistered): Failed to write reg index 0x0001: -19
> Nov 28 20:22:11 localhost kernel: ax88179_178a 2-3:1.0 enp2s0u3 (unregistered): Failed to write reg index 0x0002: -19
> 
> The reason is that although the device is detached, normal stop and
> unbind operations are commanded from the driver. These operations are
> not necessary in this situation, so avoid these logs when the device is
> detached if the result of the operation is -ENODEV and if the new flag
> informing about the disconnecting status is enabled.
> 
> cc: stable@...r.kernel.org
> Fixes: e2ca90c276e1f ("ax88179_178a: ASIX AX88179_178A USB 3.0/2.0 to gigabit ethernet adapter driver")
> Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@...hat.com>
> ---
> V1 -> V2:
> - Follow the suggestions from Alan Stern and Oliver Neukum to check the
> result of the operations (-ENODEV) and not the internal state of the USB 
> layer (USB_STATE_NOTATTACHED).
> V2 -> V3
> - Add cc: stable line in the signed-off-by area.
> V3 -> V4
> - Follow the suggestions from Oliver Neukum to use only one flag when
> disconnecting and include barriers to avoid memory ordering issues.
> V4 -> V5
> - Fix my misundestanding and follow the suggestion from Alan Stern to 
> syncronize and not order the flag.
> V5 -> V6
> - Remove the unnecessary mutex. Thank you Alan for your teaching and
> patience!

Acked-by: Alan Stern <stern@...land.harvard.edu>