On Thu, Dec 29, 2022 at 02:30:04AM +0200, Laurent Pinchart wrote:
> Hi Dan,
>
> Thank you for the patch.
>
> On Mon, Nov 21, 2022 at 09:25:09AM +0000, Daniel Scally wrote:
> > At the moment, the UVC function graph is hardcoded IT -> PU -> OT.
> > To add XU support we need the ability to insert the XU descriptors
> > into the chain. To facilitate that, make the output terminal's
> > bSourceID attribute writeable so that we can configure its source.
> >
> > Signed-off-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>
> > ---
> > Changes in v2:
> >
> > - Updated the ABI Documentation to reflect the change.
> >
> > .../ABI/testing/configfs-usb-gadget-uvc | 2 +-
> > drivers/usb/gadget/function/uvc_configfs.c | 57 ++++++++++++++++++-
> > 2 files changed, 57 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc
> > index 611b23e6488d..feb3f2cc0c16 100644
> > --- a/Documentation/ABI/testing/configfs-usb-gadget-uvc
> > +++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc
> > @@ -52,7 +52,7 @@ Date: Dec 2014
> > KernelVersion: 4.0
> > Description: Default output terminal descriptors
> >
> > - All attributes read only:
> > + All attributes read only except bSourceID:
> >
> > ============== =============================================
> > iTerminal index of string descriptor
> > diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
> > index 4303a3283ba0..af4258120f9a 100644
> > --- a/drivers/usb/gadget/function/uvc_configfs.c
> > +++ b/drivers/usb/gadget/function/uvc_configfs.c
> > @@ -483,11 +483,66 @@ UVC_ATTR_RO(uvcg_default_output_, cname, aname)
> > UVCG_DEFAULT_OUTPUT_ATTR(b_terminal_id, bTerminalID, 8);
> > UVCG_DEFAULT_OUTPUT_ATTR(w_terminal_type, wTerminalType, 16);
> > UVCG_DEFAULT_OUTPUT_ATTR(b_assoc_terminal, bAssocTerminal, 8);
> > -UVCG_DEFAULT_OUTPUT_ATTR(b_source_id, bSourceID, 8);
> > UVCG_DEFAULT_OUTPUT_ATTR(i_terminal, iTerminal, 8);
> >
> > #undef UVCG_DEFAULT_OUTPUT_ATTR
> >
> > +static ssize_t uvcg_default_output_b_source_id_show(struct config_item *item,
> > + char *page)
> > +{
> > + struct config_group *group = to_config_group(item);
> > + struct f_uvc_opts *opts;
> > + struct config_item *opts_item;
> > + struct mutex *su_mutex = &group->cg_subsys->su_mutex;
> > + struct uvc_output_terminal_descriptor *cd;
> > + int result;
> > +
> > + mutex_lock(su_mutex); /* for navigating configfs hierarchy */
> > +
> > + opts_item = group->cg_item.ci_parent->ci_parent->ci_parent->ci_parent;
> > + opts = to_f_uvc_opts(opts_item);
> > + cd = &opts->uvc_output_terminal;
> > +
> > + mutex_lock(&opts->lock);
> > + result = sprintf(page, "%u\n", le8_to_cpu(cd->bSourceID));
> > + mutex_unlock(&opts->lock);
> > +
> > + mutex_unlock(su_mutex);
> > +
> > + return result;
> > +}
> > +
> > +static ssize_t uvcg_default_output_b_source_id_store(struct config_item *item,
> > + const char *page, size_t len)
> > +{
> > + struct config_group *group = to_config_group(item);
> > + struct f_uvc_opts *opts;
> > + struct config_item *opts_item;
> > + struct mutex *su_mutex = &group->cg_subsys->su_mutex;
> > + struct uvc_output_terminal_descriptor *cd;
> > + int result;
> > + u8 num;
> > +
> > + mutex_lock(su_mutex); /* for navigating configfs hierarchy */
> > +
> > + opts_item = group->cg_item.ci_parent->ci_parent->ci_parent->ci_parent;
> > + opts = to_f_uvc_opts(opts_item);
> > + cd = &opts->uvc_output_terminal;
> > +
> > + result = kstrtou8(page, 0, &num);
> > + if (result)
> > + return result;
> > +
> > + mutex_lock(&opts->lock);
> > + cd->bSourceID = num;
> > + mutex_unlock(&opts->lock);
> > +
> > + mutex_unlock(su_mutex);
> > +
> > + return len;
> > +}
> > +UVC_ATTR(uvcg_default_output_, b_source_id, bSourceID);
>
> Feel free to shoot this idea down if it's a bad one: given that the
> bSourceID attributes serve to create a pipeline by linking entities,
> would it make sense to model these links with symlinks ?
I forgot to mention that this would handle the bSourceID attribute
automatically, avoiding mistakes. But maybe we're over-engineering all
this...
> > +
> > static struct configfs_attribute *uvcg_default_output_attrs[] = {
> > &uvcg_default_output_attr_b_terminal_id,
> > &uvcg_default_output_attr_w_terminal_type,
--
Regards,
Laurent Pinchart
