On Tue, Nov 07, 2023 at 10:17:43AM +0100, Uwe Kleine-König wrote:
> On today's platforms the benefit of platform_driver_probe() isn't that
> relevant any more. It allows to drop some code after booting (or module
> loading) for .probe() and discard the .remove() function completely if
> the driver is built-in. This typically saves a few 100k.
>
> The downside of platform_driver_probe() is that the driver cannot be
> bound and unbound at runtime which is ancient and also slightly
> complicates testing. There are also thoughts to deprecate
> platform_driver_probe() because it adds some complexity in the driver
> core for little gain. Also many drivers don't use it correctly. This
> driver for example misses to mark the driver struct with __refdata which
> is needed to suppress a (W=1) modpost warning:
>
> WARNING: modpost: drivers/video/fbdev/atmel_lcdfb: section mismatch in reference: atmel_lcdfb_driver+0x4 (section: .data) -> atmel_lcdfb_remove (section: .exit.text)
>
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> ---
> drivers/video/fbdev/atmel_lcdfb.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/video/fbdev/atmel_lcdfb.c b/drivers/video/fbdev/atmel_lcdfb.c
> index a908db233409..b218731ef732 100644
> --- a/drivers/video/fbdev/atmel_lcdfb.c
> +++ b/drivers/video/fbdev/atmel_lcdfb.c
> @@ -1017,7 +1017,7 @@ static int atmel_lcdfb_of_init(struct atmel_lcdfb_info *sinfo)
> return ret;
> }
>
> -static int __init atmel_lcdfb_probe(struct platform_device *pdev)
> +static int atmel_lcdfb_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> struct fb_info *info;
> @@ -1223,7 +1223,7 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev)
> return ret;
> }
>
> -static int __exit atmel_lcdfb_remove(struct platform_device *pdev)
> +static int atmel_lcdfb_remove(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> struct fb_info *info = dev_get_drvdata(dev);
> @@ -1301,7 +1301,8 @@ static int atmel_lcdfb_resume(struct platform_device *pdev)
> #endif
>
> static struct platform_driver atmel_lcdfb_driver = {
> - .remove = __exit_p(atmel_lcdfb_remove),
> + .probe = atmel_lcdfb_probe,
> + .remove = atmel_lcdfb_remove,
> .suspend = atmel_lcdfb_suspend,
> .resume = atmel_lcdfb_resume,
> .driver = {
> @@ -1310,7 +1311,7 @@ static struct platform_driver atmel_lcdfb_driver = {
> },
> };
>
> -module_platform_driver_probe(atmel_lcdfb_driver, atmel_lcdfb_probe);
> +module_platform_driver(atmel_lcdfb_driver, );
>
> MODULE_DESCRIPTION("AT91 LCD Controller framebuffer driver");
> MODULE_AUTHOR("Nicolas Ferre <nicolas.ferre@xxxxxxxxx>");
> --
> 2.42.0
>
For what it's worth, this introduces a warning when building certain
configurations (such as ARCH=arm multi_v5_defconfig) with clang:
WARNING: modpost: vmlinux: section mismatch in reference: atmel_lcdfb_probe+0x6c4 (section: .text) -> atmel_lcdfb_init_fbinfo (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: atmel_lcdfb_probe+0x858 (section: .text) -> atmel_lcdfb_fix (section: .init.rodata)
This appears to be legitimate to me? GCC did not warn but I assume that
is due to differences in inlining. The following clears it up for me,
should I send a standalone patch or should this be squashed in?
Cheers,
Nathan
diff --git a/drivers/video/fbdev/atmel_lcdfb.c b/drivers/video/fbdev/atmel_lcdfb.c
index 88c75ae7d315..9e391e5eaf9d 100644
--- a/drivers/video/fbdev/atmel_lcdfb.c
+++ b/drivers/video/fbdev/atmel_lcdfb.c
@@ -220,7 +220,7 @@ static inline void atmel_lcdfb_power_control(struct atmel_lcdfb_info *sinfo, int
}
}
-static const struct fb_fix_screeninfo atmel_lcdfb_fix __initconst = {
+static const struct fb_fix_screeninfo atmel_lcdfb_fix = {
.type = FB_TYPE_PACKED_PIXELS,
.visual = FB_VISUAL_TRUECOLOR,
.xpanstep = 0,
@@ -841,7 +841,7 @@ static void atmel_lcdfb_task(struct work_struct *work)
atmel_lcdfb_reset(sinfo);
}
-static int __init atmel_lcdfb_init_fbinfo(struct atmel_lcdfb_info *sinfo)
+static int atmel_lcdfb_init_fbinfo(struct atmel_lcdfb_info *sinfo)
{
struct fb_info *info = sinfo->info;
int ret = 0;
