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usb: gadget: u_audio: fix calculations for small bInterval

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If bInterval is 1, then p_interval is 8000 and p_interval_mil is 8E9,
which is too big for a 32-bit value.  While the storage is indeed
64-bit, this value is used as the divisor in do_div() which will
truncate it into a uint32_t leading to incorrect calculated values.

Switch back to keeping the base value in struct snd_uac_chip which fits
easily into an int, meaning that the division can be done in two steps
with the divisor fitting safely into a uint32_t on both steps.

Fixes: 6fec018a7e ("usb: gadget: u_audio.c: Adding Playback Pitch ctl for sync playback")
Tested-by: Pavel Hofman <pavel.hofman@ivitera.com>
Signed-off-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20220104183243.718258-1-john@metanate.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
John Keeping 2022-01-04 18:32:42 +00:00 committed by Greg Kroah-Hartman
parent 92ef98a4ca
commit f2f69bf65d
1 changed files with 13 additions and 11 deletions
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24
drivers/usb/gadget/function/u_audio.c
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@ -76,8 +76,8 @@ struct snd_uac_chip {
struct snd_pcm *pcm;
/* pre-calculated values for playback iso completion */
unsigned long long p_interval_mil;
unsigned long long p_residue_mil;
unsigned int p_interval;
unsigned int p_framesize;
};
@ -194,21 +194,24 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
* If there is a residue from this division, add it to the
* residue accumulator.
*/
unsigned long long p_interval_mil = uac->p_interval * 1000000ULL;
pitched_rate_mil = (unsigned long long)
params->p_srate * prm->pitch;
div_result = pitched_rate_mil;
do_div(div_result, uac->p_interval_mil);
do_div(div_result, uac->p_interval);
do_div(div_result, 1000000);
frames = (unsigned int) div_result;
pr_debug("p_srate %d, pitch %d, interval_mil %llu, frames %d\n",
params->p_srate, prm->pitch, uac->p_interval_mil, frames);
params->p_srate, prm->pitch, p_interval_mil, frames);
p_pktsize = min_t(unsigned int,
uac->p_framesize * frames,
ep->maxpacket);
if (p_pktsize < ep->maxpacket) {
residue_frames_mil = pitched_rate_mil - frames * uac->p_interval_mil;
residue_frames_mil = pitched_rate_mil - frames * p_interval_mil;
p_pktsize_residue_mil = uac->p_framesize * residue_frames_mil;
} else
p_pktsize_residue_mil = 0;
@ -222,11 +225,11 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
* size and decrease the accumulator.
*/
div_result = uac->p_residue_mil;
do_div(div_result, uac->p_interval_mil);
do_div(div_result, uac->p_interval);
do_div(div_result, 1000000);
if ((unsigned int) div_result >= uac->p_framesize) {
req->length += uac->p_framesize;
uac->p_residue_mil -= uac->p_framesize *
uac->p_interval_mil;
uac->p_residue_mil -= uac->p_framesize * p_interval_mil;
pr_debug("increased req length to %d\n", req->length);
}
pr_debug("remains uac->p_residue_mil %llu\n", uac->p_residue_mil);
@ -591,7 +594,7 @@ int u_audio_start_playback(struct g_audio *audio_dev)
unsigned int factor;
const struct usb_endpoint_descriptor *ep_desc;
int req_len, i;
unsigned int p_interval, p_pktsize;
unsigned int p_pktsize;
ep = audio_dev->in_ep;
prm = &uac->p_prm;
@ -612,11 +615,10 @@ int u_audio_start_playback(struct g_audio *audio_dev)
/* pre-compute some values for iso_complete() */
uac->p_framesize = params->p_ssize *
num_channels(params->p_chmask);
p_interval = factor / (1 << (ep_desc->bInterval - 1));
uac->p_interval_mil = (unsigned long long) p_interval * 1000000;
uac->p_interval = factor / (1 << (ep_desc->bInterval - 1));
p_pktsize = min_t(unsigned int,
uac->p_framesize *
(params->p_srate / p_interval),
(params->p_srate / uac->p_interval),
ep->maxpacket);
req_len = p_pktsize;