linux/drivers/usb/gadget
Daniel Mack 9bb87f1689 usb: gadget: f_uac2: send reasonably sized packets
The UAC2 function driver currently responds to all packets at all times
with wMaxPacketSize packets. That results in way too fast audio
playback as the function driver (which is in fact supposed to define
the audio stream pace) delivers as fast as it can.

Fix this by sizing each packet correctly with the following steps:

 a) Set the packet's size by dividing the nominal data rate by the
    playback endpoint's interval.

 b) If there is a residual value from the calculation in a), add
    it to a accumulator to keep track of it across packets.

 c) If the accumulator has gathered at least the number of bytes
    that are needed for one sample frame, increase the packet size.

This way, the packet size calculation will get rid of any kind of
imprecision that would otherwise occur with a simple division over
time.

Some of the variables that are needed while processing each packet
are pre-computed for performance reasons.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
2014-09-02 09:28:00 -05:00
..
function usb: gadget: f_uac2: send reasonably sized packets 2014-09-02 09:28:00 -05:00
legacy usb: gadget: use $(srctree) instead of $(PWD) for includes 2014-08-29 15:53:46 -05:00
udc usb: gadget: USB_RENESAS_USBHS_UDC should depend on HAS_DMA 2014-09-02 09:16:45 -05:00
composite.c usb: gadget: composite: dequeue cdev->req before free its buffer 2014-09-02 09:16:45 -05:00
config.c usb: gadget: always update HS/SS descriptors and create a copy of them 2012-10-31 15:09:44 +02:00
configfs.c usb: patches for v3.17 merge window 2014-07-21 11:33:41 -07:00
configfs.h usb: gadget: OS descriptors: provide interface directory names 2014-06-19 10:06:48 -05:00
epautoconf.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
functions.c usb: gadget: add a forward pointer from usb_function to its "instance" 2013-01-21 20:52:46 +02:00
Kconfig usb: gadget: f_uac1: convert to new function interface with backward compatibility 2014-08-20 14:04:54 -05:00
Makefile usb: gadget: use $(srctree) instead of $(PWD) for includes 2014-08-29 15:53:46 -05:00
u_f.c usb: gadget: only GPL drivers in the gadget and phy framework 2014-04-21 14:07:12 -05:00
u_f.h usb: gadget: FunctionFS: share VLA macros with all usb gadget files 2014-05-14 09:37:27 -05:00
u_os_desc.h usb: gadget: u_os_desc: helper functions for accessing ext prop buffer 2014-07-10 08:36:51 -05:00
usbstring.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00