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Date:   Sun, 4 Jun 2023 17:24:36 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Andrzej Hajda <andrzej.hajda@intel.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Liu Ying <victor.liu@nxp.com>, Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@gmail.com>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Nick Terrell <terrelln@fb.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Shawn Guo <shawnguo@kernel.org>,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/2] drm/bridge: imx: fix mixed module-builtin object
Message-ID: <20230604142436.GE7754@pendragon.ideasonboard.com>
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 <20230604132602.GB7754@pendragon.ideasonboard.com>
 <CAK7LNATv_t+4pt6-RJxX3DyNgyXN=nEoVHQ8zMRtgrtB_4VJ5Q@mail.gmail.com>
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On Sun, Jun 04, 2023 at 10:45:07PM +0900, Masahiro Yamada wrote:
> On Sun, Jun 4, 2023 at 10:26 PM Laurent Pinchart wrote:
> > On Sun, Jun 04, 2023 at 04:57:12PM +0900, Masahiro Yamada wrote:
> > > With CONFIG_DRM_IMX8QM_LDB=m and CONFIG_DRM_IMX8QXP_LDB=y (or vice
> > > versa), imx-ldb-helper.o is linked to a module and also to vmlinux
> > > even though the expected CFLAGS are different between builtins and
> > > modules.
> > >
> > > This is the same situation as fixed by commit 637a642f5ca5 ("zstd:
> > > Fixing mixed module-builtin objects").
> > >
> > > Split imx-ldb-helper.c into a separate module.
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > ---
> > >
> > > Changes in v2:
> > >  - Add a separate module instead of making the functions static inline
> > >
> > >  drivers/gpu/drm/bridge/imx/Kconfig          |  5 +++++
> > >  drivers/gpu/drm/bridge/imx/Makefile         |  5 +++--
> > >  drivers/gpu/drm/bridge/imx/imx-ldb-helper.c | 20 ++++++++++++++++++++
> > >  3 files changed, 28 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/bridge/imx/Kconfig b/drivers/gpu/drm/bridge/imx/Kconfig
> > > index 608f47f41bcd..9fae28db6aa7 100644
> > > --- a/drivers/gpu/drm/bridge/imx/Kconfig
> > > +++ b/drivers/gpu/drm/bridge/imx/Kconfig
> > > @@ -1,9 +1,13 @@
> > >  if ARCH_MXC || COMPILE_TEST
> > >
> > > +config DRM_IMX_LDB_HELPER
> > > +     tristate
> > > +
> > >  config DRM_IMX8QM_LDB
> > >       tristate "Freescale i.MX8QM LVDS display bridge"
> > >       depends on OF
> > >       depends on COMMON_CLK
> > > +     select DRM_IMX_LDB_HELPER
> > >       select DRM_KMS_HELPER
> > >       help
> > >         Choose this to enable the internal LVDS Display Bridge(LDB) found in
> > > @@ -13,6 +17,7 @@ config DRM_IMX8QXP_LDB
> > >       tristate "Freescale i.MX8QXP LVDS display bridge"
> > >       depends on OF
> > >       depends on COMMON_CLK
> > > +     select DRM_IMX_LDB_HELPER
> > >       select DRM_KMS_HELPER
> > >       help
> > >         Choose this to enable the internal LVDS Display Bridge(LDB) found in
> > > diff --git a/drivers/gpu/drm/bridge/imx/Makefile b/drivers/gpu/drm/bridge/imx/Makefile
> > > index aa90ec8d5433..5fc821278693 100644
> > > --- a/drivers/gpu/drm/bridge/imx/Makefile
> > > +++ b/drivers/gpu/drm/bridge/imx/Makefile
> > > @@ -1,7 +1,8 @@
> > > -imx8qm-ldb-objs := imx-ldb-helper.o imx8qm-ldb-drv.o
> > > +obj-$(CONFIG_DRM_IMX_LDB_HELPER) += imx-ldb-helper.o
> > > +imx8qm-ldb-objs := imx8qm-ldb-drv.o
> > >  obj-$(CONFIG_DRM_IMX8QM_LDB) += imx8qm-ldb.o
> > >
> > > -imx8qxp-ldb-objs := imx-ldb-helper.o imx8qxp-ldb-drv.o
> > > +imx8qxp-ldb-objs := imx8qxp-ldb-drv.o
> > >  obj-$(CONFIG_DRM_IMX8QXP_LDB) += imx8qxp-ldb.o
> > >
> > >  obj-$(CONFIG_DRM_IMX8QXP_PIXEL_COMBINER) += imx8qxp-pixel-combiner.o
> > > diff --git a/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c b/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c
> > > index 7338b84bc83d..7382cb1fbfd7 100644
> > > --- a/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c
> > > +++ b/drivers/gpu/drm/bridge/imx/imx-ldb-helper.c
> > > @@ -4,8 +4,10 @@
> > >   * Copyright 2019,2020,2022 NXP
> > >   */
> > >
> > > +#include <linux/export.h>
> > >  #include <linux/media-bus-format.h>
> > >  #include <linux/mfd/syscon.h>
> > > +#include <linux/module.h>
> > >  #include <linux/of.h>
> > >  #include <linux/regmap.h>
> > >
> > > @@ -15,16 +17,20 @@
> > >
> > >  #include "imx-ldb-helper.h"
> > >
> > > +#define DRIVER_NAME          "imx-ldb-helper"
> > > +
> > >  bool ldb_channel_is_single_link(struct ldb_channel *ldb_ch)
> > >  {
> > >       return ldb_ch->link_type == LDB_CH_SINGLE_LINK;
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_channel_is_single_link);
> > >
> > >  bool ldb_channel_is_split_link(struct ldb_channel *ldb_ch)
> > >  {
> > >       return ldb_ch->link_type == LDB_CH_DUAL_LINK_EVEN_ODD_PIXELS ||
> > >              ldb_ch->link_type == LDB_CH_DUAL_LINK_ODD_EVEN_PIXELS;
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_channel_is_split_link);
> > >
> > >  int ldb_bridge_atomic_check_helper(struct drm_bridge *bridge,
> > >                                  struct drm_bridge_state *bridge_state,
> > > @@ -38,6 +44,7 @@ int ldb_bridge_atomic_check_helper(struct drm_bridge *bridge,
> > >
> > >       return 0;
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_bridge_atomic_check_helper);
> > >
> > >  void ldb_bridge_mode_set_helper(struct drm_bridge *bridge,
> > >                               const struct drm_display_mode *mode,
> > > @@ -69,6 +76,7 @@ void ldb_bridge_mode_set_helper(struct drm_bridge *bridge,
> > >               break;
> > >       }
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_bridge_mode_set_helper);
> > >
> > >  void ldb_bridge_enable_helper(struct drm_bridge *bridge)
> > >  {
> > > @@ -81,6 +89,7 @@ void ldb_bridge_enable_helper(struct drm_bridge *bridge)
> > >        */
> > >       regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_bridge_enable_helper);
> > >
> > >  void ldb_bridge_disable_helper(struct drm_bridge *bridge)
> > >  {
> > > @@ -95,6 +104,7 @@ void ldb_bridge_disable_helper(struct drm_bridge *bridge)
> > >
> > >       regmap_write(ldb->regmap, ldb->ctrl_reg, ldb->ldb_ctrl);
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_bridge_disable_helper);
> > >
> > >  int ldb_bridge_attach_helper(struct drm_bridge *bridge,
> > >                            enum drm_bridge_attach_flags flags)
> > > @@ -117,6 +127,7 @@ int ldb_bridge_attach_helper(struct drm_bridge *bridge,
> > >                               ldb_ch->next_bridge, bridge,
> > >                               DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_bridge_attach_helper);
> > >
> > >  int ldb_init_helper(struct ldb *ldb)
> > >  {
> > > @@ -157,6 +168,7 @@ int ldb_init_helper(struct ldb *ldb)
> > >
> > >       return 0;
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_init_helper);
> > >
> > >  int ldb_find_next_bridge_helper(struct ldb *ldb)
> > >  {
> > > @@ -184,6 +196,7 @@ int ldb_find_next_bridge_helper(struct ldb *ldb)
> > >
> > >       return 0;
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_find_next_bridge_helper);
> > >
> > >  void ldb_add_bridge_helper(struct ldb *ldb,
> > >                          const struct drm_bridge_funcs *bridge_funcs)
> > > @@ -204,6 +217,7 @@ void ldb_add_bridge_helper(struct ldb *ldb,
> > >               drm_bridge_add(&ldb_ch->bridge);
> > >       }
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_add_bridge_helper);
> > >
> > >  void ldb_remove_bridge_helper(struct ldb *ldb)
> > >  {
> > > @@ -219,3 +233,9 @@ void ldb_remove_bridge_helper(struct ldb *ldb)
> > >               drm_bridge_remove(&ldb_ch->bridge);
> > >       }
> > >  }
> > > +EXPORT_SYMBOL_GPL(ldb_remove_bridge_helper);
> > > +
> > > +MODULE_DESCRIPTION("i.MX8 LVDS Display Bridge(LDB)/Pixel Mapper bridge helper");
> > > +MODULE_AUTHOR("Liu Ying <victor.liu@nxp.com>");
> > > +MODULE_LICENSE("GPL");
> > > +MODULE_ALIAS("platform:" DRIVER_NAME);
> >
> > Is the alias needed ? With that fixed (if needed),
> 
> I just tried to be consistent because all the modules
> in drivers/gpu/drm/bridge/imx/ have this boilerplate.
> 
> I do not know why MODULE_ALIAS() is needed, though.

Unless I'm mistaken, it's used in those drivers to help with
module auto-loading (although I wonder if it's still needed for devices
that have an I2C or DT ID table). I don't think you need it here.

> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

-- 
Regards,

Laurent Pinchart