Re: [PATCH] of: Make of framebuffer devices unique

From: Thomas Zimmermann
Date: Thu Jan 19 2023 - 04:18:21 EST

Hi

Am 19.01.23 um 10:01 schrieb Michal Suchánek:
On Thu, Jan 19, 2023 at 09:00:44AM +0100, Thomas Zimmermann wrote:
Hi Michal,

thanks for fixing this issue. But the review time was way too short. Please
see my comments below.

Am 18.01.23 um 22:46 schrieb Michal Suchánek:
On Wed, Jan 18, 2023 at 09:13:05PM +0100, Erhard F. wrote:
On Tue, 17 Jan 2023 17:58:04 +0100
Michal Suchanek <msuchanek@xxxxxxx> wrote:

Since Linux 5.19 this error is observed:

sysfs: cannot create duplicate filename '/devices/platform/of-display'

This is because multiple devices with the same name 'of-display' are
created on the same bus.

Update the code to create numbered device names for the non-boot
disaplay.

cc: linuxppc-dev@xxxxxxxxxxxxxxxx
References: https://bugzilla.kernel.org/show_bug.cgi?id=216095
Fixes: 52b1b46c39ae ("of: Create platform devices for OF framebuffers")
Reported-by: Erhard F. <erhard_f@xxxxxxxxxxx>
Suggested-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
---
drivers/of/platform.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 81c8c227ab6b..f2a5d679a324 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -525,6 +525,7 @@ static int __init of_platform_default_populate_init(void)
if (IS_ENABLED(CONFIG_PPC)) {
struct device_node *boot_display = NULL;
struct platform_device *dev;
+ int display_number = 1;
int ret;
/* Check if we have a MacOS display without a node spec */
@@ -561,10 +562,15 @@ static int __init of_platform_default_populate_init(void)
boot_display = node;
break;
}
+
for_each_node_by_type(node, "display") {
+ char *buf[14];

Another issue here: This should simply be buf[14]; not a pointer. Is 14 chars enough for the string plus a full number?

if (!of_get_property(node, "linux,opened", NULL) || node == boot_display)
continue;
- of_platform_device_create(node, "of-display", NULL);
+ ret = snprintf(buf, "of-display-%d", display_number++);

The second argument to snprintf() is sizeof(buf); the number of characters in buf.


Platform devices use a single dot (.) as separator before the index.
Counting starts at zero. See /sys/bus/platform/ for examples. Can we please
stick with that scheme? Generated names would then be of-display.0,
of-display.1, etc.

Yes, there was surprisingly no bikeshedding.

Do we also want to change the name of the device that did manage to
instantiate before?

This scheme changes the name only for those that did not in the past,
hence "of-display" and "of-display-%d", starting from 1.

I find that very confusing. It is is better to count all devices from 0. I don't expect this to be an issue for userspace. But if necessary, devfs can create softlinks to of-display.0.

Best regards
Thomas


Sure, replacing '-' with '.' is easy enough, and using the same format
for both as well.

Thanks

Michal


Best regards
Thomas



+ if (ret >= sizeof(buf))
+ continue;
+ of_platform_device_create(node, buf, NULL);
}
} else {
--
2.35.3


Thank you for the patch Michal!

It applies on 6.2-rc4 but I get this build error with my config:

Indeed, it's doubly bad.

Where is the kernel test robot when you need it?

It should not be that easy to miss this file but clearly it can happen.

I will send a fixup.

Sorry about the mess.

Thanks

Michal

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev




--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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