Thanks for the review. My motivation was slightly different from disabling the URL when the configured endpoint is untrusted or unavailable. I wanted to keep the URL QR mode while allowing the same kernel image to use a different reporting endpoint depending on the deployment.
It also allows enabling the compressed URL mode without rebuilding the kernel. With an empty CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL, the QR code contains the raw kmsg. Supplying drm.panic_qr_url= at boot instead switches it to the URL format, where the kmsg is compressed with zlib. This could be useful for a distribution or a locally built kernel image used on multiple systems: the image can keep a neutral/default configuration, while individual systems can opt into a specific panic report collector and compressed QR payload at boot time. panic_screen=user or panic_screen=kmsg only disables the URL QR mode; it does not provide a way to keep that mode while changing or enabling the reporting endpoint. The parameter is read-only after initialization, so it only selects the endpoint at boot/module load time. If keeping the URL fixed at build time is intentional policy for DRM panic, though, I'm fine with dropping the patch. Jocelyn Falempe <[email protected]> 于2026年10月3日周六 06:56写道： > > On 10/3/26 00:20, 纳西妲 · Nahida wrote: > > The base URL used for the panic QR code is currently fixed at build time > > by CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL. Changing the panic report > > endpoint therefore requires rebuilding the kernel. > > > > Add a drm.panic_qr_url module parameter to allow overriding the URL at > > boot or module load time, while keeping the Kconfig value as the > > default. > > > > Keep the parameter read-only after initialization so the panic path can > > access it without additional synchronization. > > > > Expose the configured URL to the DRM panic helper through an internal > > getter so the helper can use the runtime value when generating the QR > > code. > > The code looks good, but I think it shouldn't be allowed to change this > setting at boot time. > You can already set the drm_panic screen to "user" or "kmsg" in the > kernel command line if you don't trust the default URL, or if the URL is > no more reachable. > It introduces some complexity, and I don't really see the benefit. > > Best regards, > > -- > > Jocelyn> > > Assisted-by: LLM > > Signed-off-by: 纳西妲 · Nahida <[email protected]> > > --- > > v2: > > - Grow the formatted URL buffer to accommodate the maximum 255-byte > > runtime base URL. > > - Reject unexpectedly truncated formatted URLs. > > - Test the maximum-length runtime URL. > > > > v1: https://lore.kernel.org/r/[email protected] > > > > Tested on x86_64: > > - Full modular build with DRM=m and DRM_KMS_HELPER=m. > > - QEMU/virtio-gpu runtime override with a non-empty Kconfig default URL. > > - QEMU/virtio-gpu runtime fallback to the Kconfig default URL. > > - QEMU/virtio-gpu runtime override with an empty Kconfig default URL. > > - QEMU/virtio-gpu raw kmsg QR fallback with no configured URL. > > - QEMU/virtio-gpu runtime override with a 255-byte base URL. > > > > drivers/gpu/drm/Kconfig | 9 +++++---- > > drivers/gpu/drm/drm_panic.c | 9 +++++++++ > > drivers/gpu/drm/drm_panic_helper.c | 17 +++++++++++------ > > drivers/gpu/drm/drm_panic_internal.h | 4 ++++ > > 4 files changed, 29 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > > index 61111d50b..3d9d421f0 100644 > > --- a/drivers/gpu/drm/Kconfig > > +++ b/drivers/gpu/drm/Kconfig > > @@ -111,10 +111,11 @@ config DRM_PANIC_SCREEN_QR_CODE_URL > > string "Base URL of the QR code in the panic screen" > > depends on DRM_PANIC_SCREEN_QR_CODE > > help > > - This option sets the base URL to report the kernel panic. If it's > > set > > - the QR code will contain the URL and the kmsg compressed with zlib > > as > > - a URL parameter. If it's empty, the QR code will contain the kmsg as > > - uncompressed text only. > > + This option sets the default base URL to report the kernel panic. If > > + it's set the QR code will contain the URL and the kmsg compressed > > with > > + zlib as a URL parameter. If it's empty, the QR code will contain the > > + kmsg as uncompressed text only. It can be overridden with the > > + drm.panic_qr_url=<url> kernel parameter. > > There is a demo code in javascript, to decode and uncompress the > > kmsg > > data from the URL parameter at https://github.com/kdj0c/panic_report > > > > diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c > > index 9fe97c4ed..463544f71 100644 > > --- a/drivers/gpu/drm/drm_panic.c > > +++ b/drivers/gpu/drm/drm_panic.c > > @@ -49,6 +49,15 @@ MODULE_LICENSE("GPL"); > > static uint panic_qr_version = CONFIG_DRM_PANIC_SCREEN_QR_VERSION; > > module_param(panic_qr_version, uint, 0644); > > MODULE_PARM_DESC(panic_qr_version, "maximum version (size) of the QR > > code"); > > +static char panic_qr_url[256] = CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL; > > +module_param_string(panic_qr_url, panic_qr_url, sizeof(panic_qr_url), > > 0444); > > +MODULE_PARM_DESC(panic_qr_url, "base URL of the QR code in the panic > > screen"); > > + > > +const char *drm_panic_get_qr_url(void) > > +{ > > + return panic_qr_url; > > +} > > +EXPORT_SYMBOL_GPL(drm_panic_get_qr_url); > > #endif > > > > static enum drm_panic_type drm_panic_type = -1; > > diff --git a/drivers/gpu/drm/drm_panic_helper.c > > b/drivers/gpu/drm/drm_panic_helper.c > > index 8913c3d22..b0ea0b4e8 100644 > > --- a/drivers/gpu/drm/drm_panic_helper.c > > +++ b/drivers/gpu/drm/drm_panic_helper.c > > @@ -609,17 +609,20 @@ static void drm_panic_helper_qr_exit(void) > > stream.workspace = NULL; > > } > > > > -static int drm_panic_helper_get_qr_code_url(u8 **qr_image, unsigned int > > qr_version) > > +static int drm_panic_helper_get_qr_code_url(u8 **qr_image, unsigned int > > qr_version, > > + const char *qr_url) > > { > > struct kmsg_dump_iter iter; > > - char url[256]; > > + char url[512]; > > size_t kmsg_len, max_kmsg_size; > > char *kmsg; > > int max_qr_data_size, url_len; > > > > url_len = snprintf(url, sizeof(url), "%s?a=%s&v=%s&z=", > > - CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL, > > - utsname()->machine, utsname()->release); > > + qr_url, utsname()->machine, utsname()->release); > > + > > + if (url_len >= (int)sizeof(url)) > > + return -E2BIG; > > > > max_qr_data_size = drm_panic_helper_qr_max_data_size(qr_version, > > url_len); > > max_kmsg_size = min(MAX_ZLIB_RATIO * max_qr_data_size, > > QR_BUFFER1_SIZE); > > @@ -686,8 +689,10 @@ static int drm_panic_helper_get_qr_code_raw(u8 > > **qr_image, unsigned int qr_versi > > > > static int drm_panic_helper_get_qr_code(u8 **qr_image, unsigned int > > qr_version) > > { > > - if (strlen(CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL) > 0) > > - return drm_panic_helper_get_qr_code_url(qr_image, qr_version); > > + const char *qr_url = drm_panic_get_qr_url(); > > + > > + if (qr_url[0]) > > + return drm_panic_helper_get_qr_code_url(qr_image, qr_version, > > qr_url); > > else > > return drm_panic_helper_get_qr_code_raw(qr_image, qr_version); > > } > > diff --git a/drivers/gpu/drm/drm_panic_internal.h > > b/drivers/gpu/drm/drm_panic_internal.h > > index fe6d514a0..f33552265 100644 > > --- a/drivers/gpu/drm/drm_panic_internal.h > > +++ b/drivers/gpu/drm/drm_panic_internal.h > > @@ -14,6 +14,10 @@ struct drm_device; > > > > #ifdef CONFIG_DRM_PANIC > > > > +#if IS_ENABLED(CONFIG_DRM_PANIC_SCREEN_QR_CODE) > > +const char *drm_panic_get_qr_url(void); > > +#endif > > + > > /** > > * drm_panic_lock - protect panic printing relevant state > > * @dev: struct drm_device > > > > base-commit: 54e61ea6c492d69a1717018826d8340810c812eb >
