Re: [PATCH v1] usb:gadget: Fix issue with config_ep_by_speed function.

[Roger Quadros <rogerq@ti.com>]

Hi Pawel,

On 14/02/2020 21:55, Pawel Laszczak wrote:
>>
>> 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.
> 

I would vote for 2.

> It's only my personal opinion :) .
> 
> Felipe and Greg what is you opinion ?
> 
> Best Regards,
> Pawel
> 
>>
>> BR,
>> Thinh
> 

-- 

cheers,
-roger

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