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SubjectRe: [PATCH v1] usb:gadget: Fix issue with config_ep_by_speed function.
Date
Pawel Laszczak wrote:
> Hi,
>
>> Hi,
>>
>> Jayshri Pawar wrote:
>>> This patch adds additional parameter alt to config_ep_by_speed function.
>>> This additional parameter allows to improve this function and
>>> find proper usb_ss_ep_comp_descriptor.
>>>
>>> Problem has appeared during testing f_tcm (BOT/UAS) driver function.
>>>
>>> f_tcm function for SS use array of headers for both BOT/UAS alternate
>>> setting:
>>>
>>> static struct usb_descriptor_header *uasp_ss_function_desc[] = {
>>> (struct usb_descriptor_header *) &bot_intf_desc,
>>> (struct usb_descriptor_header *) &bot_uasp_ss_bi_desc,
>>> (struct usb_descriptor_header *) &bot_bi_ep_comp_desc,
>>> (struct usb_descriptor_header *) &bot_uasp_ss_bo_desc,
>>> (struct usb_descriptor_header *) &bot_bo_ep_comp_desc,
>>>
>>> (struct usb_descriptor_header *) &uasp_intf_desc,
>>> (struct usb_descriptor_header *) &bot_uasp_ss_bi_desc,
>>> (struct usb_descriptor_header *) &uasp_bi_ep_comp_desc,
>>> (struct usb_descriptor_header *) &uasp_bi_pipe_desc,
>>> (struct usb_descriptor_header *) &bot_uasp_ss_bo_desc,
>>> (struct usb_descriptor_header *) &uasp_bo_ep_comp_desc,
>>> (struct usb_descriptor_header *) &uasp_bo_pipe_desc,
>>> (struct usb_descriptor_header *) &uasp_ss_status_desc,
>>> (struct usb_descriptor_header *) &uasp_status_in_ep_comp_desc,
>>> (struct usb_descriptor_header *) &uasp_status_pipe_desc,
>>> (struct usb_descriptor_header *) &uasp_ss_cmd_desc,
>>> (struct usb_descriptor_header *) &uasp_cmd_comp_desc,
>>> (struct usb_descriptor_header *) &uasp_cmd_pipe_desc,
>>> NULL,
>>> };
>>>
>>> The first 5 descriptors are associated with BOT alternate setting,
>>> and others are associated with UAS.
>>>
>>> During handling UAS alternate setting f_tcm drivr invokes
>>> config_ep_by_speed and this function sets incorrect companion endpoint
>>> descriptor in usb_ep object.
>>>
>>> Instead setting ep->comp_desc to uasp_bi_ep_comp_desc function in this
>>> case set ep->comp_desc to bot_uasp_ss_bi_desc.
>>>
>>> This is due to the fact that it search endpoint based on endpoint
>>> address:
>>>
>>> for_each_ep_desc(speed_desc, d_spd) {
>>> chosen_desc = (struct usb_endpoint_descriptor *)*d_spd;
>>> if (chosen_desc->bEndpoitAddress == _ep->address)
>>> goto ep_found;
>>> }
>>>
>>> And in result it uses the descriptor from BOT alternate setting
>>> instead UAS.
>>>
>>> Finally, it causes that controller driver during enabling endpoints
>>> detect that just enabled endpoint for bot.
>>>
>>> Signed-off-by: Jayshri Pawar <jpawar@cadence.com>
>>> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
>>> ---
>>> drivers/usb/gadget/composite.c | 46 ++++++++++++++------
>>> drivers/usb/gadget/function/f_acm.c | 7 +--
>>> drivers/usb/gadget/function/f_ecm.c | 7 +--
>>> drivers/usb/gadget/function/f_eem.c | 4 +-
>>> drivers/usb/gadget/function/f_fs.c | 3 +-
>>> drivers/usb/gadget/function/f_hid.c | 4 +-
>>> drivers/usb/gadget/function/f_loopback.c | 2 +-
>>> drivers/usb/gadget/function/f_mass_storage.c | 5 ++-
>>> drivers/usb/gadget/function/f_midi.c | 2 +-
>>> drivers/usb/gadget/function/f_ncm.c | 7 +--
>>> drivers/usb/gadget/function/f_obex.c | 4 +-
>>> drivers/usb/gadget/function/f_phonet.c | 4 +-
>>> drivers/usb/gadget/function/f_rndis.c | 7 +--
>>> drivers/usb/gadget/function/f_serial.c | 4 +-
>>> drivers/usb/gadget/function/f_sourcesink.c | 11 +++--
>>> drivers/usb/gadget/function/f_subset.c | 4 +-
>>> drivers/usb/gadget/function/f_tcm.c | 36 +++++++--------
>>> drivers/usb/gadget/function/f_uac1_legacy.c | 2 +-
>>> drivers/usb/gadget/function/f_uvc.c | 5 ++-
>>> drivers/usb/gadget/function/u_audio.c | 4 +-
>>> include/linux/usb/composite.h | 2 +-
>>> 21 files changed, 99 insertions(+), 71 deletions(-)
>>>
>> I think we should create a new function and keep the old
>> config_ep_by_speed() for default alt-setting (e.i. have
>> config_ep_by_speed calls the new function with default alt-setting 0).
>> This way, we can keep compatibility with old function drivers and
>> minimize changes. At least that's what we did.
>>
> I don't think we need the separate function.
> If we set last parameter alt=0 then this function will work in the same way as old one.
>

I wasn't talking about that. This patch modifies the
config_ep_by_speed() parameters, which requires to make a change to
every function driver of the kernel, and all in a single patch. This
makes it difficult to backport this fix. The only function driver that
you really need this fix for is f_tcm because of the stream eps right?

You could just add a function like

int config_ep_by_speed_and_alt(struct usb_gadget *g, struct
usb_function *f, unsigned int alt, struct usb_ep *_ep);


Then redefine config_ep_by_speed() to use it

int config_ep_by_speed(struct usb_gadget *g,
                      struct usb_function *f,
                      struct usb_ep *_ep)
{
       return config_ep_by_speed_and_alt(g, f, 0, _ep);
}

This way, 1) you can split this patch, 2) you only need to make a fix to
f_tcm, 3) this fix can be backported much easier.

Anyways, this is just a suggestion. It's up to the maintainers to decide.

BR,
Thinh

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