Hi Maxime,

Thank you for the patch.

On Wednesday, 7 February 2018 16:26:43 EET Maxime Ripard wrote:
> The Cadence MIPI-CSI2 TX controller is an hardware block meant to be used
> as a bridge between pixel interfaces and a CSI-2 bus.
> 
> It supports operating with an internal or external D-PHY, with up to 4
> lanes, or without any D-PHY. The current code only supports the former
> case.
> 
> While the virtual channel input on the pixel interface can be directly
> mapped to CSI2, the datatype input is actually a selection signal (3-bits)
> mapping to a table of up to 8 preconfigured datatypes/formats (programmed
> at start-up)
> 
> The block supports up to 8 input datatypes.

The DT bindings document four input streams. Does this mean that, to use more 
than 4 data types, a system would need to transmit multiplexed streams on a 
single input stream with the 3 selection bits qualifying each sample ? That 
would be an interesting setup.

> Signed-off-by: Maxime Ripard <maxime.rip...@bootlin.com>
> ---
>  drivers/media/platform/cadence/Kconfig       |   6 +
>  drivers/media/platform/cadence/Makefile      |   1 +
>  drivers/media/platform/cadence/cdns-csi2tx.c | 582 ++++++++++++++++++++++++
>  3 files changed, 589 insertions(+)
>  create mode 100644 drivers/media/platform/cadence/cdns-csi2tx.c
> 
> diff --git a/drivers/media/platform/cadence/Kconfig
> b/drivers/media/platform/cadence/Kconfig index d1b6bbb6a0eb..db49328ee8b2
> 100644
> --- a/drivers/media/platform/cadence/Kconfig
> +++ b/drivers/media/platform/cadence/Kconfig
> @@ -9,4 +9,10 @@ config VIDEO_CADENCE_CSI2RX
>       depends on VIDEO_V4L2_SUBDEV_API
>       select V4L2_FWNODE
> 
> +config VIDEO_CADENCE_CSI2TX
> +     tristate "Cadence MIPI-CSI2 TX Controller"
> +     depends on MEDIA_CONTROLLER
> +     depends on VIDEO_V4L2_SUBDEV_API
> +     select V4L2_FWNODE

A bit of documentation maybe ?

>  endif
> diff --git a/drivers/media/platform/cadence/Makefile
> b/drivers/media/platform/cadence/Makefile index 99a4086b7448..7fe992273162
> 100644
> --- a/drivers/media/platform/cadence/Makefile
> +++ b/drivers/media/platform/cadence/Makefile
> @@ -1 +1,2 @@
>  obj-$(CONFIG_VIDEO_CADENCE_CSI2RX)   += cdns-csi2rx.o
> +obj-$(CONFIG_VIDEO_CADENCE_CSI2TX)   += cdns-csi2tx.o
> diff --git a/drivers/media/platform/cadence/cdns-csi2tx.c
> b/drivers/media/platform/cadence/cdns-csi2tx.c new file mode 100644
> index 000000000000..3cc58c26d226
> --- /dev/null
> +++ b/drivers/media/platform/cadence/cdns-csi2tx.c
> @@ -0,0 +1,582 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Driver for Cadence MIPI-CSI2 TX Controller
> + *
> + * Copyright (C) 2017 Cadence Design Systems Inc.
> + */
> +
> +#include <linux/atomic.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +#include <media/v4l2-ctrls.h>
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-fwnode.h>
> +#include <media/v4l2-subdev.h>
> +
> +#define CSI2TX_DEVICE_CONFIG_REG     0x00
> +
> +#define CSI2TX_CONFIG_REG            0x20
> +#define CSI2TX_CONFIG_CFG_REQ                        BIT(2)
> +#define CSI2TX_CONFIG_SRST_REQ                       BIT(1)
> +
> +#define CSI2TX_DPHY_CFG_REG          0x28
> +#define CSI2TX_DPHY_CFG_CLK_RESET            BIT(16)
> +#define CSI2TX_DPHY_CFG_LANE_RESET(n)                BIT((n) + 12)
> +#define CSI2TX_DPHY_CFG_MODE_MASK            GENMASK(9, 8)
> +#define CSI2TX_DPHY_CFG_MODE_LPDT            (2 << 8)
> +#define CSI2TX_DPHY_CFG_MODE_HS                      (1 << 8)
> +#define CSI2TX_DPHY_CFG_MODE_ULPS            (0 << 8)
> +#define CSI2TX_DPHY_CFG_CLK_ENABLE           BIT(4)
> +#define CSI2TX_DPHY_CFG_LANE_ENABLE(n)               BIT(n)
> +
> +#define CSI2TX_DPHY_CLK_WAKEUP_REG   0x2c
> +#define CSI2TX_DPHY_CLK_WAKEUP_ULPS_CYCLES(n)        ((n) & 0xffff)
> +
> +#define CSI2TX_DT_CFG_REG(n)         (0x80 + (n) * 8)
> +#define CSI2TX_DT_CFG_DT(n)                  (((n) & 0x3f) << 2)
> +
> +#define CSI2TX_DT_FORMAT_REG(n)              (0x84 + (n) * 8)
> +#define CSI2TX_DT_FORMAT_BYTES_PER_LINE(n)   (((n) & 0xffff) << 16)
> +#define CSI2TX_DT_FORMAT_MAX_LINE_NUM(n)     ((n) & 0xffff)
> +
> +#define CSI2TX_STREAM_IF_CFG_REG(n)  (0x100 + (n) * 4)
> +#define CSI2TX_STREAM_IF_CFG_FILL_LEVEL(n)   ((n) & 0x1f)
> +
> +#define CSI2RX_LANES_MAX     4
> +#define CSI2TX_STREAMS_MAX   4
> +
> +enum csi2tx_pads {
> +     CSI2TX_PAD_SOURCE,
> +     CSI2TX_PAD_SINK_STREAM0,
> +     CSI2TX_PAD_SINK_STREAM1,
> +     CSI2TX_PAD_SINK_STREAM2,
> +     CSI2TX_PAD_SINK_STREAM3,
> +     CSI2TX_PAD_MAX,
> +};
> +
> +struct csi2tx_fmt {
> +     u32     mbus;
> +     u32     dt;
> +     u32     bpp;
> +};
> +
> +struct csi2tx_priv {
> +     struct device                   *dev;
> +     atomic_t                        count;
> +
> +     void __iomem                    *base;
> +
> +     struct clk                      *esc_clk;
> +     struct clk                      *p_clk;
> +     struct clk                      *pixel_clk[CSI2TX_STREAMS_MAX];
> +
> +     struct v4l2_subdev              subdev;
> +     struct v4l2_async_notifier      notifier;
> +     struct media_pad                pads[CSI2TX_PAD_MAX];
> +     struct v4l2_mbus_framefmt       pad_fmts[CSI2TX_PAD_MAX];
> +
> +     bool                            has_internal_dphy;
> +     u8                              lanes[CSI2RX_LANES_MAX];
> +     unsigned int                    num_lanes;
> +     unsigned int                    max_lanes;
> +     unsigned int                    max_streams;
> +
> +     /* Remote source */
> +     struct v4l2_async_subdev        asd;
> +     struct v4l2_subdev              *sink_subdev;
> +     int                             sink_pad;
> +};
> +
> +static const struct csi2tx_fmt csi2tx_formats[] = {
> +     {
> +             .mbus   = MEDIA_BUS_FMT_UYVY8_1X16,
> +             .bpp    = 2,
> +             .dt     = 0x1e,
> +     },
> +     {
> +             .mbus   = MEDIA_BUS_FMT_RGB888_1X24,
> +             .bpp    = 3,
> +             .dt     = 0x24,
> +     },
> +};
> +
> +static const struct v4l2_mbus_framefmt fmt_default = {
> +     .width          = 320,
> +     .height         = 180,

That's a pretty small default resolution. Is there any reason for not using a 
more common format ?

> +     .code           = MEDIA_BUS_FMT_RGB888_1X24,
> +     .field          = V4L2_FIELD_NONE,
> +     .colorspace     = V4L2_COLORSPACE_DEFAULT,
> +};
> +
> +static inline
> +struct csi2tx_priv *v4l2_subdev_to_csi2tx(struct v4l2_subdev *subdev)
> +{
> +     return container_of(subdev, struct csi2tx_priv, subdev);
> +}
> +
> +static int csi2tx_init_cfg(struct v4l2_subdev *subdev,
> +                        struct v4l2_subdev_pad_config *cfg)
> +{
> +     struct csi2tx_priv *csi2tx = v4l2_subdev_to_csi2tx(subdev);
> +     unsigned int i;
> +
> +     for (i = 0; i < subdev->entity.num_pads; i++)
> +             csi2tx->pad_fmts[i] = fmt_default;

.init_cfg() should initialize the formats stored in the cfg structure. The 
active formats stored in your driver-specific structure should be initialized 
at probe time.

> +
> +     return 0;
> +}
> +
> +static const struct csi2tx_fmt *csitx_get_fmt_from_mbus(struct
> v4l2_mbus_framefmt *mfmt)
> +{
> +     int i;

i can be unsigned.

> +
> +     if (!mfmt)
> +             return NULL;
> +
> +     for (i = 0; i < ARRAY_SIZE(csi2tx_formats); i++)
> +             if (csi2tx_formats[i].mbus == mfmt->code)
> +                     return &csi2tx_formats[i];
> +
> +     return NULL;
> +}
> +
> +static int csi2tx_enum_mbus_code(struct v4l2_subdev *subdev,
> +                              struct v4l2_subdev_pad_config *cfg,
> +                              struct v4l2_subdev_mbus_code_enum *code)
> +{
> +     if (code->pad || code->index >= ARRAY_SIZE(csi2tx_formats))
> +             return -EINVAL;
> +
> +     code->code = csi2tx_formats[code->index].mbus;
> +
> +     return 0;
> +}
> +
> +static int csi2tx_get_pad_format(struct v4l2_subdev *subdev,
> +                              struct v4l2_subdev_pad_config *cfg,
> +                              struct v4l2_subdev_format *fmt)
> +{
> +     struct csi2tx_priv *csi2tx = v4l2_subdev_to_csi2tx(subdev);
> +
> +     fmt->format = csi2tx->pad_fmts[fmt->pad];
> +
> +     return 0;
> +}
> +
> +static int csi2tx_set_pad_format(struct v4l2_subdev *subdev,
> +                              struct v4l2_subdev_pad_config *cfg,
> +                              struct v4l2_subdev_format *fmt)
> +{
> +     struct csi2tx_priv *csi2tx = v4l2_subdev_to_csi2tx(subdev);
> +
> +     csi2tx->pad_fmts[fmt->pad] = fmt->format;

Doesn't the IP have frame width or height limitations ? Or format limitations 
?

> +     return 0;
> +}
> +
> +static const struct v4l2_subdev_pad_ops csi2tx_pad_ops = {
> +     .enum_mbus_code = csi2tx_enum_mbus_code,
> +     .get_fmt        = csi2tx_get_pad_format,
> +     .init_cfg       = csi2tx_init_cfg,
> +     .set_fmt        = csi2tx_set_pad_format,
> +};
> +
> +static void csi2tx_reset(struct csi2tx_priv *csi2tx)
> +{
> +     writel(CSI2TX_CONFIG_SRST_REQ, csi2tx->base + CSI2TX_CONFIG_REG);
> +
> +     usleep_range(10, 20);

As for the RX driver, udelay() might be better. Same comment for the other 
small delays below.

> +}
> +
> +static int csi2tx_start(struct csi2tx_priv *csi2tx)
> +{
> +     struct media_entity *entity = &csi2tx->subdev.entity;
> +     struct media_link *link;
> +     u32 reg;
> +     int i;

i can be unsigned.

> +
> +     /*
> +      * We're not the first users, there's no need to enable the
> +      * whole controller.
> +      */
> +     if (atomic_inc_return(&csi2tx->count) > 1)
> +             return 0;

Same comment as for the RX driver regarding the potential race condition here.

> +
> +     csi2tx_reset(csi2tx);
> +
> +     writel(CSI2TX_CONFIG_CFG_REQ, csi2tx->base + CSI2TX_CONFIG_REG);
> +
> +     usleep_range(10, 20);
> +
> +     writel(CSI2TX_DPHY_CLK_WAKEUP_ULPS_CYCLES(32),
> +            csi2tx->base + CSI2TX_DPHY_CLK_WAKEUP_REG);
> +
> +     /* Put our lanes (clock and data) out of reset */
> +     reg = CSI2TX_DPHY_CFG_CLK_RESET | CSI2TX_DPHY_CFG_MODE_LPDT;
> +     for (i = 0; i < csi2tx->num_lanes; i++)
> +             reg |= CSI2TX_DPHY_CFG_LANE_RESET(csi2tx->lanes[i]);
> +     writel(reg, csi2tx->base + CSI2TX_DPHY_CFG_REG);
> +
> +     usleep_range(10, 20);
> +
> +     /* Enable our (clock and data) lanes */
> +     reg |= CSI2TX_DPHY_CFG_CLK_ENABLE;
> +     for (i = 0; i < csi2tx->num_lanes; i++)
> +             reg |= CSI2TX_DPHY_CFG_LANE_ENABLE(csi2tx->lanes[i]);
> +     writel(reg, csi2tx->base + CSI2TX_DPHY_CFG_REG);
> +
> +     usleep_range(10, 20);
> +
> +     /* Switch to HS mode */
> +     reg &= ~CSI2TX_DPHY_CFG_MODE_MASK;
> +     writel(reg | CSI2TX_DPHY_CFG_MODE_HS,
> +            csi2tx->base + CSI2TX_DPHY_CFG_REG);
> +
> +     usleep_range(10, 20);
> +
> +     /*
> +      * Create a static mapping between the CSI virtual channels
> +      * and the input streams.
> +      *
> +      * This should be enhanced, but v4l2 lacks the support for
> +      * changing that mapping dynamically at the moment.
> +      */
> +     list_for_each_entry(link, &entity->links, list) {

I assume that you're protected from the race with userspace setting up links 
by the fact that upper layer should have called media_pipeline_start(). I 
would mention that explicitly in the comment.

> +             struct v4l2_mbus_framefmt *mfmt;
> +             const struct csi2tx_fmt *fmt;
> +             unsigned int stream;
> +             int pad_idx = -1;
> +
> +             /* Only consider our enabled input pads */
> +             for (i = CSI2TX_PAD_SINK_STREAM0; i < CSI2TX_PAD_MAX; i++) {
> +                     struct media_pad *pad = &csi2tx->pads[i];
> +
> +                     if ((pad == link->sink) &&
> +                         (link->flags & MEDIA_LNK_FL_ENABLED)) {
> +                             pad_idx = i;
> +                             break;
> +                     }
> +             }
> +
> +             if (pad_idx < 0)
> +                     continue;
> +
> +             mfmt = &csi2tx->pad_fmts[i];
> +             fmt = csitx_get_fmt_from_mbus(mfmt);

This can return NULL.

> +             stream = pad_idx - CSI2TX_PAD_SINK_STREAM0;
> +
> +             /*
> +              * We use the stream ID there, but it's wrong.
> +              *
> +              * A stream could very well send a data type that is
> +              * not equal to its stream ID. We need to find a
> +              * proper way to address it.
> +              */
> +             writel(CSI2TX_DT_CFG_DT(fmt->dt),
> +                    csi2tx->base + CSI2TX_DT_CFG_REG(stream));
> +
> +             writel(CSI2TX_DT_FORMAT_BYTES_PER_LINE(mfmt->width * fmt->bpp) |
> +                    CSI2TX_DT_FORMAT_MAX_LINE_NUM(mfmt->height + 1),
> +                    csi2tx->base + CSI2TX_DT_FORMAT_REG(stream));
> +
> +             /*
> +              * TODO: This needs to be calculated based on the
> +              * output CSI2 clock rate.
> +              */
> +             writel(CSI2TX_STREAM_IF_CFG_FILL_LEVEL(4),
> +                    csi2tx->base + CSI2TX_STREAM_IF_CFG_REG(stream));
> +     }
> +
> +     /* Disable the configuration mode */
> +     writel(0, csi2tx->base + CSI2TX_CONFIG_REG);
> +
> +     return v4l2_subdev_call(csi2tx->sink_subdev, video, s_stream, true);

I'm pretty sure you should start the sink before the transmitter, otherwise it 
won't be able to synchronize to the LP-11 state.

> +}
> +
> +static int csi2tx_stop(struct csi2tx_priv *csi2tx)
> +{
> +     /*
> +      * Let the last user turn off the lights
> +      */
> +     if (!atomic_dec_and_test(&csi2tx->count))
> +             return 0;
> +
> +     writel(CSI2TX_CONFIG_CFG_REQ | CSI2TX_CONFIG_SRST_REQ,
> +            csi2tx->base + CSI2TX_CONFIG_REG);
> +
> +     return 0;
> +}
> +
> +static int csi2tx_s_stream(struct v4l2_subdev *subdev, int enable)
> +{
> +     struct csi2tx_priv *csi2tx = v4l2_subdev_to_csi2tx(subdev);
> +     int ret;
> +
> +     if (enable)
> +             ret = csi2tx_start(csi2tx);
> +     else
> +             ret = csi2tx_stop(csi2tx);

How about

        if (enable)
                return csi2tx_start(csi2tx);
        else
                return csi2tx_stop(csi2tx);

> +
> +     return ret;
> +}
> +
> +static const struct v4l2_subdev_video_ops csi2tx_video_ops = {
> +     .s_stream       = csi2tx_s_stream,
> +};
> +
> +static const struct v4l2_subdev_ops csi2tx_subdev_ops = {
> +     .pad            = &csi2tx_pad_ops,
> +     .video          = &csi2tx_video_ops,
> +};
> +
> +static int csi2tx_async_bound(struct v4l2_async_notifier *notifier,
> +                           struct v4l2_subdev *s_subdev,
> +                           struct v4l2_async_subdev *asd)
> +{
> +     struct v4l2_subdev *subdev = notifier->sd;
> +     struct csi2tx_priv *csi2tx = v4l2_subdev_to_csi2tx(subdev);
> +
> +     csi2tx->sink_pad = media_entity_get_fwnode_pad(&s_subdev->entity,
> +                                                    s_subdev->fwnode,
> +                                                    MEDIA_PAD_FL_SINK);
> +     if (csi2tx->sink_pad < 0) {
> +             dev_err(csi2tx->dev, "Couldn't find input pad for subdev %s\n",
> +                     s_subdev->name);
> +             return csi2tx->sink_pad;
> +     }
> +
> +     csi2tx->sink_subdev = s_subdev;
> +
> +     dev_dbg(csi2tx->dev, "Bound %s pad: %d\n", s_subdev->name,
> +             csi2tx->sink_pad);
> +
> +     return media_create_pad_link(&csi2tx->sink_subdev->entity,
> +                                  csi2tx->sink_pad,
> +                                  &csi2tx->subdev.entity, 0,
> +                                  MEDIA_LNK_FL_ENABLED |
> +                                  MEDIA_LNK_FL_IMMUTABLE);
> +}
> +
> +static const struct v4l2_async_notifier_operations csi2tx_notifier_ops = {
> +     .bound          = csi2tx_async_bound,
> +};
> +
> +static int csi2tx_get_resources(struct csi2tx_priv *csi2tx,
> +                             struct platform_device *pdev)
> +{
> +     struct resource *res;
> +     u32 reg;

Should you name the variable dev_cfg to make it a bit more explicit ?

> +     int i;

i can be unsigned.

> +
> +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +     csi2tx->base = devm_ioremap_resource(&pdev->dev, res);
> +     if (IS_ERR(csi2tx->base)) {
> +             dev_err(&pdev->dev, "Couldn't map our registers\n");

devm_ioremap_resource() prints an error message, you don't need to duplicate 
that.

> +             return PTR_ERR(csi2tx->base);
> +     }
> +
> +     csi2tx->p_clk = devm_clk_get(&pdev->dev, "p_clk");
> +     if (IS_ERR(csi2tx->p_clk)) {
> +             dev_err(&pdev->dev, "Couldn't get p_clk\n");
> +             return PTR_ERR(csi2tx->p_clk);
> +     }
> +
> +     csi2tx->esc_clk = devm_clk_get(&pdev->dev, "esc_clk");
> +     if (IS_ERR(csi2tx->esc_clk)) {
> +             dev_err(&pdev->dev, "Couldn't get the esc_clk\n");
> +             return PTR_ERR(csi2tx->esc_clk);
> +     }
> +
> +     clk_prepare_enable(csi2tx->p_clk);
> +     reg = readl(csi2tx->base + CSI2TX_DEVICE_CONFIG_REG);
> +     clk_disable_unprepare(csi2tx->p_clk);
> +
> +     csi2tx->max_lanes = (reg & 7);

No need for outer parentheses.

> +     if (csi2tx->max_lanes > 4) {
> +             dev_err(&pdev->dev, "Invalid number of lanes: %u\n",
> +                     csi2tx->max_lanes);
> +             return -EINVAL;
> +     }
> +
> +     csi2tx->max_streams = ((reg >> 4) & 7);

No need for outer parentheses.

> +     if (csi2tx->max_streams > CSI2TX_STREAMS_MAX) {
> +             dev_err(&pdev->dev, "Invalid number of streams: %u\n",
> +                     csi2tx->max_streams);
> +             return -EINVAL;
> +     }
> +
> +     csi2tx->has_internal_dphy = (reg & BIT(3)) ? true : false;
> +
> +     for (i = 0; i < csi2tx->max_streams; i++) {
> +             char clk_name[16];
> +
> +             snprintf(clk_name, sizeof(clk_name), "pixel_if%u_clk", i);
> +             csi2tx->pixel_clk[i] = devm_clk_get(&pdev->dev, clk_name);
> +             if (IS_ERR(csi2tx->pixel_clk[i])) {
> +                     dev_err(&pdev->dev, "Couldn't get clock %s\n",
> +                             clk_name);
> +                     return PTR_ERR(csi2tx->pixel_clk[i]);
> +             }
> +     }
> +
> +     return 0;
> +}
> +
> +static int csi2tx_check_lanes(struct csi2tx_priv *csi2tx)
> +{
> +     struct v4l2_fwnode_endpoint v4l2_ep;
> +     struct device_node *ep;
> +     int ret;
> +
> +     ep = of_graph_get_endpoint_by_regs(csi2tx->dev->of_node, 0, 0);
> +     if (!ep)
> +             return -EINVAL;
> +
> +     ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(ep), &v4l2_ep);
> +     if (ret) {
> +             dev_err(csi2tx->dev, "Could not parse v4l2 endpoint\n");
> +             goto out;
> +     }
> +
> +     if (v4l2_ep.bus_type != V4L2_MBUS_CSI2) {
> +             dev_err(csi2tx->dev, "Unsupported media bus type: 0x%x\n",
> +                     v4l2_ep.bus_type);
> +             ret = -EINVAL;
> +             goto out;
> +     }
> +
> +     csi2tx->num_lanes = v4l2_ep.bus.mipi_csi2.num_data_lanes;
> +     if (csi2tx->num_lanes > csi2tx->max_lanes) {
> +             dev_err(csi2tx->dev,
> +                     "Current configuration uses more lanes than 
> supported\n");
> +             ret = -EINVAL;
> +             goto out;
> +     }
> +
> +     memcpy(csi2tx->lanes, v4l2_ep.bus.mipi_csi2.data_lanes,
> +            sizeof(csi2tx->lanes));
> +
> +out:
> +     of_node_put(ep);
> +     return ret;
> +}
> +
> +static int csi2tx_parse_dt(struct csi2tx_priv *csi2tx)
> +{
> +     struct fwnode_handle *fwh;
> +     struct device_node *ep;
> +
> +     ep = of_graph_get_endpoint_by_regs(csi2tx->dev->of_node, 0, 0);
> +     if (!ep)
> +             return -EINVAL;
> +
> +     fwh = of_fwnode_handle(ep);
> +     csi2tx->asd.match.fwnode.fwnode =
> fwnode_graph_get_remote_port_parent(fwh);
> +     csi2tx->asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
> +     of_node_put(ep);
> +
> +     csi2tx->notifier.subdevs = devm_kzalloc(csi2tx->dev,
> +                                             
> sizeof(*csi2tx->notifier.subdevs),
> +                                             GFP_KERNEL);
> +     if (!csi2tx->notifier.subdevs)
> +             return -ENOMEM;
> +
> +     csi2tx->notifier.subdevs[0] = &csi2tx->asd;
> +     csi2tx->notifier.num_subdevs = 1;
> +     csi2tx->notifier.ops = &csi2tx_notifier_ops;
> +
> +     return v4l2_async_subdev_notifier_register(&csi2tx->subdev,
> +                                                &csi2tx->notifier);
> +}
> +
> +static int csi2tx_probe(struct platform_device *pdev)
> +{
> +     struct csi2tx_priv *csi2tx;
> +     int i, ret;

I think i can be unsigned.

> +
> +     csi2tx = kzalloc(sizeof(*csi2tx), GFP_KERNEL);
> +     if (!csi2tx)
> +             return -ENOMEM;
> +     platform_set_drvdata(pdev, csi2tx);
> +     csi2tx->dev = &pdev->dev;
> +
> +     ret = csi2tx_get_resources(csi2tx, pdev);
> +     if (ret)
> +             goto err_free_priv;
> +
> +     ret = csi2tx_parse_dt(csi2tx);
> +     if (ret)
> +             goto err_free_priv;
> +
> +     v4l2_subdev_init(&csi2tx->subdev, &csi2tx_subdev_ops);
> +     csi2tx->subdev.owner = THIS_MODULE;
> +     csi2tx->subdev.dev = &pdev->dev;
> +     csi2tx->subdev.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> +     v4l2_set_subdevdata(&csi2tx->subdev, &pdev->dev);
> +     snprintf(csi2tx->subdev.name, V4L2_SUBDEV_NAME_SIZE, "%s.%s",
> +              KBUILD_MODNAME, dev_name(&pdev->dev));
> +
> +     ret = csi2tx_check_lanes(csi2tx);
> +     if (ret)
> +             goto err_free_priv;
> +
> +     /* Create our media pads */
> +     csi2tx->subdev.entity.function = MEDIA_ENT_F_PROC_VIDEO_PIXEL_FORMATTER;

Same comment as for the RX driver, MEDIA_ENT_F_VID_IF_BRIDGE is better in my 
opinion.

> +     csi2tx->pads[CSI2TX_PAD_SOURCE].flags = MEDIA_PAD_FL_SOURCE;
> +     for (i = CSI2TX_PAD_SINK_STREAM0; i < CSI2TX_PAD_MAX; i++)
> +             csi2tx->pads[i].flags = MEDIA_PAD_FL_SINK;
> +
> +     ret = media_entity_pads_init(&csi2tx->subdev.entity, CSI2TX_PAD_MAX,
> +                                  csi2tx->pads);
> +     if (ret)
> +             goto err_free_priv;
> +
> +     ret = v4l2_async_register_subdev(&csi2tx->subdev);
> +     if (ret < 0)
> +             goto err_free_priv;
> +
> +     dev_info(&pdev->dev,
> +              "Probed CSI2TX with %u/%u lanes, %u streams, %s D-PHY\n",
> +              csi2tx->num_lanes, csi2tx->max_lanes, csi2tx->max_streams,
> +              csi2tx->has_internal_dphy ? "internal" : "no");
> +
> +     return 0;
> +
> +err_free_priv:
> +     kfree(csi2tx);
> +     return ret;
> +}

[snip]

-- 
Regards,

Laurent Pinchart

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