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    SubjectRe: [PATCH 2/6] drm: dsi: Let host and device specify supported bus
    Hi Paul.

    On Mon, Jul 27, 2020 at 06:46:09PM +0200, Paul Cercueil wrote:
    > The current MIPI DSI framework can very well be used to support MIPI DBI
    > panels. In order to add support for the various bus types supported by
    > DBI, the DRM panel drivers should specify the bus type they will use,
    > and the DSI host drivers should specify the bus types they are
    > compatible with.
    >
    > The DSI host driver can then use the information provided by the DBI/DSI
    > device driver, such as the bus type and the number of lanes, to
    > configure its hardware properly.
    >
    > Signed-off-by: Paul Cercueil <paul@crapouillou.net>
    > ---
    > drivers/gpu/drm/drm_mipi_dsi.c | 9 +++++++++
    > include/drm/drm_mipi_dsi.h | 12 ++++++++++++
    > 2 files changed, 21 insertions(+)
    >
    > diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
    > index 5dd475e82995..11ef885de765 100644
    > --- a/drivers/gpu/drm/drm_mipi_dsi.c
    > +++ b/drivers/gpu/drm/drm_mipi_dsi.c
    > @@ -281,6 +281,9 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
    > {
    > struct device_node *node;
    >
    > + if (WARN_ON_ONCE(!host->bus_types))
    > + host->bus_types = MIPI_DEVICE_TYPE_DSI;
    > +
    So all 14 users need to specify bus_types.
    Seems doable.

    > for_each_available_child_of_node(host->dev->of_node, node) {
    > /* skip nodes without reg property */
    > if (!of_find_property(node, "reg", NULL))
    > @@ -323,6 +326,12 @@ int mipi_dsi_attach(struct mipi_dsi_device *dsi)
    > {
    > const struct mipi_dsi_host_ops *ops = dsi->host->ops;
    >
    > + if (WARN_ON_ONCE(!dsi->bus_type))
    > + dsi->bus_type = MIPI_DEVICE_TYPE_DSI;
    We have ~50 users of mipi_dsi_attach() - doable. But a bit more work.

    > +
    > + if (!(dsi->bus_type & dsi->host->bus_types))
    > + return -EINVAL;
    > +
    > if (!ops || !ops->attach)
    > return -ENOSYS;
    >
    > diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
    > index 360e6377e84b..65d2961fc054 100644
    > --- a/include/drm/drm_mipi_dsi.h
    > +++ b/include/drm/drm_mipi_dsi.h
    > @@ -63,6 +63,14 @@ struct mipi_dsi_packet {
    > int mipi_dsi_create_packet(struct mipi_dsi_packet *packet,
    > const struct mipi_dsi_msg *msg);
    >
    > +/* MIPI bus types */
    If you define this as an enum then kernel-doc syntax will be picked up.
    See for example: enum drm_driver_feature

    > +#define MIPI_DEVICE_TYPE_DSI BIT(0)
    > +#define MIPI_DEVICE_TYPE_DBI_SPI_MODE1 BIT(1)
    > +#define MIPI_DEVICE_TYPE_DBI_SPI_MODE2 BIT(2)
    > +#define MIPI_DEVICE_TYPE_DBI_SPI_MODE3 BIT(3)
    > +#define MIPI_DEVICE_TYPE_DBI_M6800 BIT(4)
    > +#define MIPI_DEVICE_TYPE_DBI_I8080 BIT(5)
    > +
    > /**
    > * struct mipi_dsi_host_ops - DSI bus operations
    > * @attach: attach DSI device to DSI host
    > @@ -94,11 +102,13 @@ struct mipi_dsi_host_ops {
    > * struct mipi_dsi_host - DSI host device
    > * @dev: driver model device node for this DSI host
    > * @ops: DSI host operations
    > + * @bus_types: Bitmask of supported MIPI bus types
    Please add some kind of reference to MIPI_DEVICE_TYPE_* - so the reader
    knows for sure this is the bits used here.

    > * @list: list management
    > */
    > struct mipi_dsi_host {
    > struct device *dev;
    > const struct mipi_dsi_host_ops *ops;
    > + unsigned int bus_types;
    Use u32. Shorter and we know this is 32 bits wide.

    > struct list_head list;
    > };
    >
    > @@ -162,6 +172,7 @@ struct mipi_dsi_device_info {
    > * @host: DSI host for this peripheral
    > * @dev: driver model device node for this peripheral
    > * @name: DSI peripheral chip type
    > + * @bus_type: MIPI bus type (MIPI_DEVICE_TYPE_DSI/...)
    > * @channel: virtual channel assigned to the peripheral
    > * @format: pixel format for video mode
    > * @lanes: number of active data lanes
    > @@ -178,6 +189,7 @@ struct mipi_dsi_device {
    > struct device dev;
    >
    > char name[DSI_DEV_NAME_SIZE];
    > + unsigned int bus_type;
    Use u32.

    > unsigned int channel;
    > unsigned int lanes;
    > enum mipi_dsi_pixel_format format;
    > --
    > 2.27.0

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