From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lb1-smtp-cloud6.xs4all.net ([194.109.24.24]:54405 "EHLO lb1-smtp-cloud6.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750917AbbG0Uis (ORCPT ); Mon, 27 Jul 2015 16:38:48 -0400 Message-ID: <55B696D0.2000700@xs4all.nl> Date: Mon, 27 Jul 2015 22:38:40 +0200 From: Hans Verkuil MIME-Version: 1.0 To: Antti Palosaari , linux-media@vger.kernel.org Subject: Re: [PATCHv2 8/9] hackrf: add support for transmitter References: <1437030298-20944-1-git-send-email-crope@iki.fi> <1437030298-20944-9-git-send-email-crope@iki.fi> <55A91474.4000801@xs4all.nl> <55B692D3.2070601@iki.fi> In-Reply-To: <55B692D3.2070601@iki.fi> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 07/27/2015 10:21 PM, Antti Palosaari wrote: > On 07/17/2015 05:43 PM, Hans Verkuil wrote: >> On 07/16/2015 09:04 AM, Antti Palosaari wrote: >>> HackRF SDR device has both receiver and transmitter. There is limitation >>> that receiver and transmitter cannot be used at the same time >>> (half-duplex operation). That patch implements transmitter support to >>> existing receiver only driver. >>> >>> Cc: Hans Verkuil >>> Signed-off-by: Antti Palosaari >>> --- >>> drivers/media/usb/hackrf/hackrf.c | 787 +++++++++++++++++++++++++++----------- >>> 1 file changed, 572 insertions(+), 215 deletions(-) >>> >> >> >>> @@ -611,8 +751,15 @@ static int hackrf_queue_setup(struct vb2_queue *vq, >>> unsigned int *nplanes, unsigned int sizes[], void *alloc_ctxs[]) >>> { >>> struct hackrf_dev *dev = vb2_get_drv_priv(vq); >>> + struct usb_interface *intf = dev->intf; >>> + int ret; >>> >>> - dev_dbg(dev->dev, "nbuffers=%d\n", *nbuffers); >>> + dev_dbg(&intf->dev, "nbuffers=%d\n", *nbuffers); >>> + >>> + if (test_and_set_bit(QUEUE_SETUP, &dev->flags)) { >>> + ret = -EBUSY; >>> + goto err; >>> + } >> >> This doesn't work. The bit is only cleared when start_streaming fails or >> stop_streaming is called. But the application can also call REQBUFS again >> or just close the file handle, and then QUEUE_SETUP should also be cleared. >> >> But why is this here in the first place? It doesn't seem to do anything >> useful (except mess up the v4l2-compliance tests). >> >> I've removed it and it now seems to work OK. > > It is there to block simultaneous use of receiver and transmitter. > Device could operate only single mode at the time - receiving or > transmitting. Driver shares streaming buffers. > > Any idea how I can easily implement correct blocking? Since each video_device struct has its own vb2_queue I wouldn't put the check here. Instead, put the check in the start_streaming callback. And the check is easy enough: if you want to start capturing, then call vb2_is_streaming(&tx_vb2_queue). If you want to start output, then call vb2_is_streaming(&rx_vb2_queue). If the other 'side' is streaming, then return EBUSY. It's perfectly valid to allocate the buffers, but actually streaming is an exclusive operation. Regards, Hans