RE: [PATCH v2] usb: gadget: f_midi: Fixing wMaxPacketSize exceeded issue during MIDI bind retries

[Alim Akhtar]

Hello Selvarasu,

> -----Original Message-----
> From: Selvarasu Ganesan <selvarasu.g@xxxxxxxxxxx>
> Sent: Saturday, January 18, 2025 11:32 AM
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> stable@xxxxxxxxxxxxxxx
> Subject: [PATCH v2] usb: gadget: f_midi: Fixing wMaxPacketSize exceeded
> issue during MIDI bind retries
> 
> The current implementation sets the wMaxPacketSize of bulk in/out
> endpoints to 1024 bytes at the end of the f_midi_bind function. However, in
> cases where there is a failure in the first midi bind attempt, consider
> rebinding. This scenario may encounter an f_midi_bind issue due to the
> previous bind setting the bulk endpoint's wMaxPacketSize to 1024 bytes,
> which exceeds the ep->maxpacket_limit where configured dwc3 TX/RX
> FIFO's maxpacket size of 512 bytes for IN/OUT endpoints in support HS
> speed only.
> 
> Here the term "rebind" in this context refers to attempting to bind the MIDI
> function a second time in certain scenarios. The situations where rebinding is
> considered include:
> 
>  * When there is a failure in the first UDC write attempt, which may be
>    caused by other functions bind along with MIDI.
>  * Runtime composition change : Example : MIDI,ADB to MIDI. Or MIDI to
>    MIDI,ADB.
> 
> This commit addresses this issue by resetting the wMaxPacketSize before
> endpoint claim. And here there is no need to reset all values in the usb
> endpoint descriptor structure, as all members except wMaxPacketSize and
> bEndpointAddress have predefined values.
> 
> This ensures that restores the endpoint to its expected configuration, and
> preventing conflicts with value of ep->maxpacket_limit. It also aligns with the
> approach used in other function drivers, which treat endpoint descriptors as
> if they were full speed before endpoint claim.
> 
> Fixes: 46decc82ffd5 ("usb: gadget: unconditionally allocate hs/ss descriptor in
> bind operation")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Selvarasu Ganesan <selvarasu.g@xxxxxxxxxxx>
> ---
Reviewed-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx>

[Snip]
> 2.17.1