Hi,
On 08/29/2014 08:13 AM, Jassi Brar wrote:
> +/*
> + * 5512.5Hz is going to need the maximum number of elements (80),
> + * in the length-pattern loop, among standard ALSA supported rates.
> + */
> +#define MAX_LOOP_LEN 80
> +
> struct uac2_rtd_params {
> struct snd_uac2_chip *uac2; /* parent chip */
> bool ep_enabled; /* if the ep is enabled */
> @@ -80,6 +87,9 @@ struct uac2_rtd_params {
> unsigned max_psize;
> struct uac2_req ureq[USB_XFERS];
>
> + unsigned pattern[MAX_LOOP_LEN];
> + unsigned plen; /* valid entries in pattern[] */
> +
> spinlock_t lock;
> };
>
You're doing this for both directions, while only the capture side needs
such treatment.
> +/*
> + * Find optimal pattern of payloads for a given number
> + * of samples and maximum sync period (in ms) over which
> + * we have to distribute them uniformly.
> + */
> +static unsigned
> +get_pattern(unsigned samples, unsigned sync, unsigned *pt)
> +{
> + unsigned n, x = 0, i = 0, p = samples % sync;
> +
> + do {
> + x += p;
> + n = samples / sync;
> + if (x >= sync) {
> + n += 1;
> + x -= sync;
> + }
> + if (pt)
> + pt[i] = n;
> + i++;
> + } while (x);
> +
> + return i;
> +}
>
> static int
> afunc_set_alt(struct usb_function *fn, unsigned intf, unsigned alt)
> {
> @@ -1097,11 +1136,35 @@ afunc_set_alt(struct usb_function *fn, unsigned intf, unsigned alt)
> if (intf == agdev->as_out_intf) {
> ep = agdev->out_ep;
> prm = &uac2->c_prm;
> + prm->plen = 1;
> + prm->pattern[0] = prm->max_psize;
> config_ep_by_speed(gadget, fn, ep);
> agdev->as_out_alt = alt;
> } else if (intf == agdev->as_in_intf) {
> + struct f_uac2_opts *opts = agdev_to_uac2_opts(agdev);
> + unsigned intvl, rate;
> +
> + if (gadget->speed == USB_SPEED_FULL)
> + intvl = (1 << (fs_epin_desc.bInterval - 1)) * 1000;
> + else
> + intvl = (1 << (hs_epin_desc.bInterval - 1)) * 125;
> +
> + rate = opts->p_srate;
> + if (rate == 5512) { /* which implies 5512.5 practically */
> + rate = 55125;
> + intvl *= 10;
> + }
> +
Well, I'd say that Alan's approach as implemented in my v6 is still more
comprehensible for anyone who'll try to understand this later, and it
doesn't make any assumption on run time values. Plus, it only adds 5
unsigned ints to struct snd_uac2_chip, while your version blows up
struct uac2_rtd_params by 81 ints.
But it's also a matter of taste, so I guess it's ultimately up to Felipe
now.
Thanks,
Daniel
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