On 07/28/2015 11:17 AM, Peter Chen wrote: > According to USB Audio Device 2.0 Spec, Ch4.10.1.1: > wMaxPacketSize is defined as follows: > Maximum packet size this endpoint is capable of sending or receiving > when this configuration is selected. > This is determined by the audio bandwidth constraints of the endpoint. > > In current code, the wMaxPacketSize is defined as the maximum packet size > for ISO endpoint, and it will let the host reserve much more space than > it really needs, so that we can't let more endpoints work together at > one frame. > > We find this issue when we try to let 4 f_uac2 gadgets work together [1] > at FS connection. > > [1]http://www.spinics.net/lists/linux-usb/msg123478.html > > Cc: andrzej.p@xxxxxxxxxxx > Cc: Daniel Mack <zonque@xxxxxxxxx> > Cc: tiwai@xxxxxxx > Cc: <stable@xxxxxxxxxxxxxxx> #v3.18+ > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx> Looks good to me now! I currently don't have hardware to test this on, though. Acked-by: Daniel Mack <zonque@xxxxxxxxx> Thanks, Daniel > --- > > Changes for v5: > - Add additional parameters 'is_playback' for helper > - Add const for parameter 'struct f_uac2_opts *uac2_opts' > - Put all three int variables at one line > - Fix the CodeStyle problem > > Changes for v4: > - Add helper set_ep_max_packet_size to calculate max packet size > > Changes for v3: > - Consider 'bInterval' to calculate wMaxPacketSize > - playback endpoint is IN ep, and capture endpoint is OUT ep > > Changes for v2: > - Using DIV_ROUND_UP to calculate max packet size > > drivers/usb/gadget/function/f_uac2.c | 31 +++++++++++++++++++++++++++++-- > 1 file changed, 29 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c > index 5318615..fa93d79 100644 > --- a/drivers/usb/gadget/function/f_uac2.c > +++ b/drivers/usb/gadget/function/f_uac2.c > @@ -975,6 +975,29 @@ free_ep(struct uac2_rtd_params *prm, struct usb_ep *ep) > "%s:%d Error!\n", __func__, __LINE__); > } > > +static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts, > + struct usb_endpoint_descriptor *ep_desc, > + unsigned int factor, bool is_playback) > +{ > + int chmask, srate, ssize; > + u16 max_packet_size; > + > + if (is_playback) { > + chmask = uac2_opts->p_chmask; > + srate = uac2_opts->p_srate; > + ssize = uac2_opts->p_ssize; > + } else { > + chmask = uac2_opts->c_chmask; > + srate = uac2_opts->c_srate; > + ssize = uac2_opts->c_ssize; > + } > + > + max_packet_size = num_channels(chmask) * ssize * > + DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > +} > + > static int > afunc_bind(struct usb_configuration *cfg, struct usb_function *fn) > { > @@ -1070,10 +1093,14 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn) > uac2->p_prm.uac2 = uac2; > uac2->c_prm.uac2 = uac2; > > + /* Calculate wMaxPacketSize according to audio bandwidth */ > + set_ep_max_packet_size(uac2_opts, &fs_epin_desc, 1000, true); > + set_ep_max_packet_size(uac2_opts, &fs_epout_desc, 1000, false); > + set_ep_max_packet_size(uac2_opts, &hs_epin_desc, 8000, true); > + set_ep_max_packet_size(uac2_opts, &hs_epout_desc, 8000, false); > + > hs_epout_desc.bEndpointAddress = fs_epout_desc.bEndpointAddress; > - hs_epout_desc.wMaxPacketSize = fs_epout_desc.wMaxPacketSize; > hs_epin_desc.bEndpointAddress = fs_epin_desc.bEndpointAddress; > - hs_epin_desc.wMaxPacketSize = fs_epin_desc.wMaxPacketSize; > > ret = usb_assign_descriptors(fn, fs_audio_desc, hs_audio_desc, NULL); > if (ret) > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
