On 2017-05-02 17:21, Philipp Zabel wrote: > On Sat, 2017-04-29 at 23:42 +0200, Peter Rosin wrote: >> On 2017-04-29 23:29, Peter Rosin wrote: >>> On 2017-04-28 16:13, Philipp Zabel wrote: >>>> This driver can handle SoC internal and external video bus multiplexers, >>>> controlled by mux controllers provided by the mux controller framework, >>>> such as MMIO register bitfields or GPIOs. The subdevice passes through >>>> the mbus configuration of the active input to the output side. >>>> >>>> Signed-off-by: Sascha Hauer <s.ha...@pengutronix.de> >>>> Signed-off-by: Philipp Zabel <p.za...@pengutronix.de> >>>> Signed-off-by: Steve Longerbeam <steve_longerb...@mentor.com> >>>> --- >>>> This has been last sent as part of the i.MX media series. >>>> >>>> Changes since https://patchwork.kernel.org/patch/9647869/: >>>> - Split out the actual mux operation to be provided by the mux controller >>>> framework [1]. GPIO and MMIO control can be provided by individual mux >>>> controller drivers [2][3]. >>>> [1] https://patchwork.kernel.org/patch/9695837/ >>>> [2] https://patchwork.kernel.org/patch/9695839/ >>>> [3] https://patchwork.kernel.org/patch/9704509/ >>>> - Shortened 'video-multiplexer' to 'video-mux', replaced all instances of >>>> vidsw with video_mux. >>>> - Made the mux inactive by default, only activated by user interaction. >>>> - Added CONFIG_OF and CONFIG_MULTIPLEXER dependencies. >>>> - Reuse subdev.entity.num_pads instead of keeping our own count. >>>> - Removed implicit link disabling. Instead, trying to enable a second >>>> sink pad link yields -EBUSY. >>>> - Merged _async_init into _probe. >>>> - Removed superfluous pad index check from _set_format. >>>> - Added is_source_pad helper to tell source and sink pads apart. >>>> - Removed test for status property in endpoint nodes. Disable the remote >>>> device or sever the endpoint link to disable a sink pad. >>>> --- >>>> drivers/media/platform/Kconfig | 6 + >>>> drivers/media/platform/Makefile | 2 + >>>> drivers/media/platform/video-mux.c | 341 >>>> +++++++++++++++++++++++++++++++++++++ >>>> 3 files changed, 349 insertions(+) >>>> create mode 100644 drivers/media/platform/video-mux.c >>>> >>>> diff --git a/drivers/media/platform/Kconfig >>>> b/drivers/media/platform/Kconfig >>>> index c9106e105baba..b046a6d39fee5 100644 >>>> --- a/drivers/media/platform/Kconfig >>>> +++ b/drivers/media/platform/Kconfig >>>> @@ -74,6 +74,12 @@ config VIDEO_M32R_AR_M64278 >>>> To compile this driver as a module, choose M here: the >>>> module will be called arv. >>>> >>>> +config VIDEO_MUX >>>> + tristate "Video Multiplexer" >>>> + depends on OF && VIDEO_V4L2_SUBDEV_API && MEDIA_CONTROLLER && >>>> MULTIPLEXER >>>> + help >>>> + This driver provides support for N:1 video bus multiplexers. >>>> + >>>> config VIDEO_OMAP3 >>>> tristate "OMAP 3 Camera support" >>>> depends on VIDEO_V4L2 && I2C && VIDEO_V4L2_SUBDEV_API && ARCH_OMAP3 >>>> diff --git a/drivers/media/platform/Makefile >>>> b/drivers/media/platform/Makefile >>>> index 349ddf6a69da2..fd2735ca3ff75 100644 >>>> --- a/drivers/media/platform/Makefile >>>> +++ b/drivers/media/platform/Makefile >>>> @@ -27,6 +27,8 @@ obj-$(CONFIG_VIDEO_SH_VEU) += sh_veu.o >>>> >>>> obj-$(CONFIG_VIDEO_MEM2MEM_DEINTERLACE) += m2m-deinterlace.o >>>> >>>> +obj-$(CONFIG_VIDEO_MUX) += video-mux.o >>>> + >>>> obj-$(CONFIG_VIDEO_S3C_CAMIF) += s3c-camif/ >>>> obj-$(CONFIG_VIDEO_SAMSUNG_EXYNOS4_IS) += exynos4-is/ >>>> obj-$(CONFIG_VIDEO_SAMSUNG_S5P_JPEG) += s5p-jpeg/ >>>> diff --git a/drivers/media/platform/video-mux.c >>>> b/drivers/media/platform/video-mux.c >>>> new file mode 100644 >>>> index 0000000000000..419541729f67e >>>> --- /dev/null >>>> +++ b/drivers/media/platform/video-mux.c >>>> @@ -0,0 +1,341 @@ >>>> +/* >>>> + * video stream multiplexer controlled via mux control >>>> + * >>>> + * Copyright (C) 2013 Pengutronix, Sascha Hauer <ker...@pengutronix.de> >>>> + * Copyright (C) 2016 Pengutronix, Philipp Zabel <ker...@pengutronix.de> >>> >>> 2017? >>> >>>> + * >>>> + * This program is free software; you can redistribute it and/or >>>> + * modify it under the terms of the GNU General Public License >>>> + * as published by the Free Software Foundation; either version 2 >>>> + * of the License, or (at your option) any later version. >>>> + * This program is distributed in the hope that it will be useful, >>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of >>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >>>> + * GNU General Public License for more details. >>>> + */ >>>> + >>>> +#include <linux/err.h> >>>> +#include <linux/module.h> >>>> +#include <linux/mux/consumer.h> >>>> +#include <linux/of.h> >>>> +#include <linux/of_graph.h> >>>> +#include <linux/platform_device.h> >>>> +#include <media/v4l2-async.h> >>>> +#include <media/v4l2-device.h> >>>> +#include <media/v4l2-subdev.h> >>>> +#include <media/v4l2-of.h> >>>> + >>>> +struct video_mux { >>>> + struct v4l2_subdev subdev; >>>> + struct media_pad *pads; >>>> + struct v4l2_mbus_framefmt *format_mbus; >>>> + struct v4l2_of_endpoint *endpoint; >>>> + struct mux_control *mux; >>>> + int active; >>>> +}; >>>> + >>>> +static inline struct video_mux *v4l2_subdev_to_video_mux(struct >>>> v4l2_subdev *sd) >>>> +{ >>>> + return container_of(sd, struct video_mux, subdev); >>>> +} >>>> + >>>> +static inline bool is_source_pad(struct video_mux *vmux, unsigned int pad) >>>> +{ >>>> + return pad == vmux->subdev.entity.num_pads - 1; >>>> +} >>>> + >>>> +static int video_mux_link_setup(struct media_entity *entity, >>>> + const struct media_pad *local, >>>> + const struct media_pad *remote, u32 flags) >>>> +{ >>>> + struct v4l2_subdev *sd = media_entity_to_v4l2_subdev(entity); >>>> + struct video_mux *vmux = v4l2_subdev_to_video_mux(sd); >>>> + int ret; >>>> + >>>> + /* >>>> + * The mux state is determined by the enabled sink pad link. >>>> + * Enabling or disabling the source pad link has no effect. >>>> + */ >>>> + if (is_source_pad(vmux, local->index)) >>>> + return 0; >>>> + >>>> + dev_dbg(sd->dev, "link setup '%s':%d->'%s':%d[%d]", >>>> + remote->entity->name, remote->index, local->entity->name, >>>> + local->index, flags & MEDIA_LNK_FL_ENABLED); >>>> + >>>> + if (flags & MEDIA_LNK_FL_ENABLED) { >>>> + if (vmux->active == local->index) >>> >>> Here, you shortcut the mux_control_select_trylock test and return "OK" >>> based on a driver-local variable that is intended to keep track of mux >>> ownership. >>> >>>> + return 0; >>>> + >>>> + if (vmux->active >= 0) >>> >>> Here too (and this check is not needed, the situation will be covered by >>> the mux_control_try_select call). >>> >>>> + return -EBUSY; >>>> + >>>> + dev_dbg(sd->dev, "setting %d active\n", local->index); >>>> + ret = mux_control_try_select(vmux->mux, local->index); >>>> + if (ret < 0) >>>> + return ret; >>>> + vmux->active = local->index; >>>> + } else { >>>> + if (vmux->active != local->index) >>>> + return 0; >>>> + >>>> + dev_dbg(sd->dev, "going inactive\n"); >>>> + mux_control_deselect(vmux->mux); >>> >>> But here you let go of the mux *before* you clear the driver-local >>> ownership indicator. That looks suspicious. My guess is that this is >>> "safe" because the upper layers has some serialization, but I don't >>> know. Anyway, even if there is something saving you in the upper >>> layers, it looks out of order and unneeded. I would have moved the >>> below vmux->active = -1; statement up to before the above deselect. >>> >>> With that fixed, mux usage looks good to me, so you can add an Acked- >>> by from me if you wish (goes for the bindings patch as well). >> >> Ouch, that was a bit too soon. If there is *no* serialization in the >> upper layers, this is *not* ok, even with my reordering. There must be >> only one call to mux_control_deselect, and w/o serialization there >> is a race where you might get multiple deselect calls when several >> callers makes it through the active != index check before any of them >> manages to set active = -1. That race must be taken care of! > > Thank you, I've resent a version with a mutex lock around vmux->active.
I had a bunch of ifs in the above message, so I'm not sure it's needed. I would expect there to be a lock outside somewhere in the media layer. A cursory look gets me to media-entity.c and media_entity_setup_link() which does have a mutex. But I'm no media expert, so maybe there are other ways of getting to video_mux_link_setup that I'm not aware of? If you do end up relying on external locking, a comment saying so would be nice. Or even better, some __must_hold markup if possible? Cheers, peda
