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

[Roger Quadros]

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@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.
>
> 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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