lkml.org 
[lkml]   [2022]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.16 0392/1039] usb: gadget: u_audio: fix calculations for small bInterval
    Date
    From: John Keeping <john@metanate.com>

    [ Upstream commit f2f69bf65df12176843ca11eab99949ba69e128b ]

    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: 6fec018a7e70 ("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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/usb/gadget/function/u_audio.c | 24 +++++++++++++-----------
    1 file changed, 13 insertions(+), 11 deletions(-)

    diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
    index c46400be54641..4fb05f9576a67 100644
    --- a/drivers/usb/gadget/function/u_audio.c
    +++ b/drivers/usb/gadget/function/u_audio.c
    @@ -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;
    --
    2.34.1


    \
     
     \ /
      Last update: 2022-01-25 01:13    [W:4.024 / U:0.044 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site