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usb: gadget: composite: Test get_alt() presence instead of set_alt()

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By convention (according to doc) if function does not provide
get_alt() callback composite framework should assume that it has only
altsetting 0 and should respond with error if host tries to set
other one.

After commit dd4dff8b03 ("USB: composite: Fix bug: should test
set_alt function pointer before use it")
we started checking set_alt() callback instead of get_alt().
This check is useless as we check if set_alt() is set inside
usb_add_function() and fail if it's NULL.

Let's fix this check and move comment about why we check the get
method instead of set a little bit closer to prevent future false
fixes.

Fixes: dd4dff8b03 ("USB: composite: Fix bug: should test set_alt function pointer before use it")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
This commit is contained in:
Krzysztof Opasiak 2016-12-20 19:52:16 +01:00 committed by Felipe Balbi
parent 51c1685d95
commit 7e4da3fcf7
1 changed files with 8 additions and 4 deletions
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12
drivers/usb/gadget/composite.c
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@ -1694,9 +1694,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
value = min(w_length, (u16) 1);
break;
/* function drivers must handle get/set altsetting; if there's
* no get() method, we know only altsetting zero works.
*/
/* function drivers must handle get/set altsetting */
case USB_REQ_SET_INTERFACE:
if (ctrl->bRequestType != USB_RECIP_INTERFACE)
goto unknown;
@ -1705,7 +1703,13 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
f = cdev->config->interface[intf];
if (!f)
break;
if (w_value && !f->set_alt)
/*
* If there's no get_alt() method, we know only altsetting zero
* works. There is no need to check if set_alt() is not NULL
* as we check this in usb_add_function().
*/
if (w_value && !f->get_alt)
break;
value = f->set_alt(f, w_index, w_value);
if (value == USB_GADGET_DELAYED_STATUS) {