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

[Thinh Nguyen]

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@xxxxxxxxxxx>
>>> Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
>>> ---
>>>    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,
     ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct usb_function *f,
     ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct usb_ep *_ep)
    {
     ÂÂÂÂÂÂ 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