On 07/27/2015 08:51 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> > --- > > 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 | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c > index 6d3eb8b..51ca32d 100644 > --- a/drivers/usb/gadget/function/f_uac2.c > +++ b/drivers/usb/gadget/function/f_uac2.c > @@ -987,6 +987,8 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn) > struct f_uac2_opts *uac2_opts; > struct usb_string *us; > int ret; > + u16 max_packet_size; > + struct usb_endpoint_descriptor *ep_desc; > > uac2_opts = container_of(fn->fi, struct f_uac2_opts, func_inst); > > @@ -1070,10 +1072,37 @@ 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 */ > + ep_desc = &fs_epin_desc; > + max_packet_size = num_channels(uac2_opts->p_chmask) * > + uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate, > + 1000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > + > + ep_desc = &fs_epout_desc; > + max_packet_size = num_channels(uac2_opts->c_chmask) * > + uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate, > + 1000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > + > + ep_desc = &hs_epin_desc; > + max_packet_size = num_channels(uac2_opts->p_chmask) * > + uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate, > + 8000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > + > + ep_desc = &hs_epout_desc; > + max_packet_size = num_channels(uac2_opts->c_chmask) * > + uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate, > + 8000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); Basically, the same operation is repeated 4 times here. What about factoring the code out to a helper function, so that the call site looks like this: set_ep_max_packet_size(&fs_epin_desc, uac2_opts, 1000); set_ep_max_packet_size(&fs_epout_desc, uac2_opts, 1000); set_ep_max_packet_size(&hs_epin_desc, uac2_opts, 8000); set_ep_max_packet_size(&hs_epout_desc, uac2_opts, 8000); Other than that, the patch now looks good to me! Thanks, Daniel > + > 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
