Re: [PATCH] drm/i915: Remove drm_dev_unregister() from the error path during i915_driver_register()

[Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>]

Hi Krzysztof,

On Fri, 2026-05-22 at 17:43 +0200, Krzysztof Niemiec wrote:
> During driver probe, in i915_driver_register(), if drm_dev_register()
> fails, the code enters into an error path. In it, a call to
> drm_dev_unregister() is made as part of cleanup in case drm_dev_register()
> returns an error. However, this is unnecessary, as in case of an error
> drm_dev_register() undoes its own setup in its own error path.

Doesn't this patch depend on your "drm: Set dev->registered back to false
in case of register failure"?  While each of the two touches a separate
area of responsibility, I would submit them as a series if that dependency
exists.

Thanks,
Janusz

> 
> Calling drm_dev_unregister() after a failed drm_dev_register() also
> generates a superfluous WARN_ON() from drm_client_sysrq_unregister().
> drm_client_sysrq_register() is only called in drm_dev_register() if
> there was no error in the latter. drm_dev_unregister() calls
> drm_client_sysrq_unregister() as it expects to be called after a successful
> drm_dev_register(), in which case the _sysrq_register() counterpart is
> called. However, if the call to drm_dev_register() failed,
> _sysrq_register() is never called; calling drm_dev_unregister() will
> cause _sysrq_unregister() to be called (unconditionally) with no
> corresponding _sysrq_register() call before it, which is caught in the
> aforementioned WARN_ON().
> 
> Remove the redundant call to drm_dev_unregister() in case
> drm_dev_register() returns an error.
> 
> Signed-off-by: Krzysztof Niemiec <krzysztof.niemiec@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_driver.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> index c10cab38935a..10e16002050a 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -638,7 +638,6 @@ static int i915_driver_register(struct drm_i915_private *dev_priv)
>  	if (ret) {
>  		i915_probe_error(dev_priv,
>  				 "Failed to register driver for userspace access!\n");
> -		drm_dev_unregister(&dev_priv->drm);
>  		i915_pmu_unregister(dev_priv);
>  		i915_gem_driver_unregister(dev_priv);
>  		return ret;