On Wed, 20 Jun 2018 16:39:22 +0200,
Sebastian Andrzej Siewior wrote:
>
> On 2018-06-20 14:51:12 [+0200], Takashi Iwai wrote:
> > On Tue, 19 Jun 2018 23:55:20 +0200,
> > Sebastian Andrzej Siewior wrote:
> > > - (*purb)->transfer_buffer =
> > > - kmalloc_array(subs->maxpacksize,
> > > - nr_of_packs(), GFP_KERNEL);
> > > - if (NULL == (*purb)->transfer_buffer) {
> > > + len = subs->maxpacksize * nr_of_packs();
> > > + buf = kmalloc(len, GFP_KERNEL);
> >
> > I'd keep kmalloc_array() as is, and just put subs->maxpacksize *
> > nr_of_packs() in usb_fill_int_urb(). Otherwise it's a step backward.
>
> but then we end up with two multiplications.
Yes, but it's no hot path, and the code won't bigger.
And I bet you won't notice any performance lost by that :)
> What about pulling the
> overflow-mul macro out of malloc_array() and doing this instead:
Well, it's neither smaller nor more readable...
thanks,
Takashi
>
> ----------- >8
>
> Subject: [PATCH 8/9 v2] ALSA: usx2y: usbusx2yaudio: use usb_fill_int_urb()
>
> Using usb_fill_int_urb() helps to find code which initializes an
> URB. A grep for members of the struct (like ->complete) reveal lots
> of other things, too.
>
> The "&& !(*purb)->transfer_buffer" check has been removed because the
> URB has been freshly allocated a few lines above so ->transfer_buffer
> has to be NULL here.
> The `dev' and `transfer_size' assignments have been moved from
> usX2Y_urbs_start() to usX2Y_urbs_allocate() because they don't change
> overtime.
> The multiplication via check_mul_overflow() has been extracted from
> kmalloc_array() to avoid two multiplication (one with overflow check and
> one without for the length argument). This requires to change the type
> `maxpacksize' to int so there is only one type involved in the
> multiplication.
>
> Cc: Jaroslav Kysela <perex@xxxxxxxx>
> Cc: Takashi Iwai <tiwai@xxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> sound/usb/usx2y/usbusx2y.h | 2 +-
> sound/usb/usx2y/usbusx2yaudio.c | 38 ++++++++++++++++-----------------
> 2 files changed, 20 insertions(+), 20 deletions(-)
>
> diff --git a/sound/usb/usx2y/usbusx2y.h b/sound/usb/usx2y/usbusx2y.h
> index e0f77172ce8f..2bec412589b4 100644
> --- a/sound/usb/usx2y/usbusx2y.h
> +++ b/sound/usb/usx2y/usbusx2y.h
> @@ -56,7 +56,7 @@ struct snd_usX2Y_substream {
> struct snd_pcm_substream *pcm_substream;
>
> int endpoint;
> - unsigned int maxpacksize; /* max packet size in bytes */
> + int maxpacksize; /* max packet size in bytes */
>
> atomic_t state;
> #define state_STOPPED 0
> diff --git a/sound/usb/usx2y/usbusx2yaudio.c b/sound/usb/usx2y/usbusx2yaudio.c
> index 2b833054e3b0..e5580cb59858 100644
> --- a/sound/usb/usx2y/usbusx2yaudio.c
> +++ b/sound/usb/usx2y/usbusx2yaudio.c
> @@ -425,33 +425,35 @@ static int usX2Y_urbs_allocate(struct snd_usX2Y_substream *subs)
> /* allocate and initialize data urbs */
> for (i = 0; i < NRURBS; i++) {
> struct urb **purb = subs->urb + i;
> + void *buf = NULL;
> + int len = 0;
> +
> if (*purb) {
> usb_kill_urb(*purb);
> continue;
> }
> *purb = usb_alloc_urb(nr_of_packs(), GFP_KERNEL);
> - if (NULL == *purb) {
> - usX2Y_urbs_release(subs);
> - return -ENOMEM;
> - }
> - if (!is_playback && !(*purb)->transfer_buffer) {
> + if (NULL == *purb)
> + goto err_free;
> +
> + if (!is_playback) {
> /* allocate a capture buffer per urb */
> - (*purb)->transfer_buffer =
> - kmalloc_array(subs->maxpacksize,
> - nr_of_packs(), GFP_KERNEL);
> - if (NULL == (*purb)->transfer_buffer) {
> - usX2Y_urbs_release(subs);
> - return -ENOMEM;
> - }
> + if (check_mul_overflow(subs->maxpacksize,
> + nr_of_packs(),
> + &len))
> + goto err_free;
> + buf = kmalloc(len, GFP_KERNEL);
> + if (!buf)
> + goto err_free;
> }
> - (*purb)->dev = dev;
> - (*purb)->pipe = pipe;
> + usb_fill_int_urb(*purb, dev, pipe, buf, len,
> + i_usX2Y_subs_startup, subs, 1);
> (*purb)->number_of_packets = nr_of_packs();
> - (*purb)->context = subs;
> - (*purb)->interval = 1;
> - (*purb)->complete = i_usX2Y_subs_startup;
> }
> return 0;
> +err_free:
> + usX2Y_urbs_release(subs);
> + return -ENOMEM;
> }
>
> static void usX2Y_subs_startup(struct snd_usX2Y_substream *subs)
> @@ -485,12 +487,10 @@ static int usX2Y_urbs_start(struct snd_usX2Y_substream *subs)
> unsigned long pack;
> if (0 == i)
> atomic_set(&subs->state, state_STARTING3);
> - urb->dev = usX2Y->dev;
> for (pack = 0; pack < nr_of_packs(); pack++) {
> urb->iso_frame_desc[pack].offset = subs->maxpacksize * pack;
> urb->iso_frame_desc[pack].length = subs->maxpacksize;
> }
> - urb->transfer_buffer_length = subs->maxpacksize * nr_of_packs();
> if ((err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
> snd_printk (KERN_ERR "cannot submit datapipe for urb %d, err = %d\n", i, err);
> err = -EPIPE;
> --
> 2.17.1
>
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