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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.

Thanks for clarification, now I got it. In my opinion, both solution has pros and cons
1. Original patch.
cons: introduce many change in many files
pros: we have only single API function - simpler Gadget Subsystem API

2. using config_ep_by_speed_and_alt
cons: minimal impact to other files.
pros: introduce the new API function which in fact could be omitted.

It's only my personal opinion :) .

Felipe and Greg what is you opinion ?

Best Regards,
Pawel

>
>BR,
>Thinh

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