usb: gadget: function: f_uac1: implement get_alt()

After commit 7e4da3fcf7c9 ("usb: gadget: composite:
Test get_alt() presence instead of set_alt()") f_uac1
function became broken because it doesn't have
get_alt() callback implementation and composite
framework never set altsetting 1 for audiostreaming
interface. On host site it looks like:

 [424339.017711] 21:1:1: usb_set_interface failed (-32)

Since host can't set altsetting 1, it can't start
playing audio.

In order to fix it implemented get_alt along with
minor improvements (error conditions checking)
similar to what existing f_uac2 has.

Cc: Krzysztof Opasiak <[email protected]>
Signed-off-by: Ruslan Bilovol <[email protected]>
Signed-off-by: Felipe Balbi <[email protected]>

0 files changed, 0 insertions, 0 deletions