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.hauer@xxxxxxxxxxxxxx> > >> Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > >> Signed-off-by: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx> > >> --- > >> 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 <kernel@xxxxxxxxxxxxxx> > >> + * Copyright (C) 2016 Pengutronix, Philipp Zabel <kernel@xxxxxxxxxxxxxx> > > > > 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. regards Philipp -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
