Hi,
On 1/26/22 16:54, Rafael J. Wysocki wrote:
> On Wed, Jan 26, 2022 at 2:47 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>>
>> Hi All,
>>
>> On 1/23/22 10:10, Tong Zhang wrote:
>>> when acpi=off is provided in bootarg, kernel crash with
>>>
>>> [ 1.252739] BUG: kernel NULL pointer dereference, address: 0000000000000018
>>> [ 1.258308] Call Trace:
>>> [ 1.258490] ? acpi_walk_namespace+0x147/0x147
>>> [ 1.258770] acpi_get_devices+0xe4/0x137
>>> [ 1.258921] ? drm_core_init+0xc0/0xc0 [drm]
>>> [ 1.259108] detect_thinkpad_privacy_screen+0x5e/0xa8 [drm]
>>> [ 1.259337] drm_privacy_screen_lookup_init+0xe/0xe85 [drm]
>>>
>>> The reason is that acpi_walk_namespace expects acpi related stuff
>>> initialized but in fact it wouldn't when acpi is set to off. In this case
>>> we should honor acpi=off in detect_thinkpad_privacy_screen().
>>>
>>> Signed-off-by: Tong Zhang <ztong0001@xxxxxxxxx>
>>
>> Thank you for catching this and thank you for your patch. I was about to merge
>> this, but then I realized that this might not be the best way to fix this.
>>
>> A quick grep shows 10 acpi_get_devices() calls outside of drivers/acpi,
>> and at a first glance about half of those are missing an acpi_disabled
>> check. IMHO it would be better to simply add an acpi_disabled check to
>> acpi_get_devices() itself.
>>
>> Rafael, do you agree ?
>
> Yes, I do.
Did you see my follow-up that that is not going to work because
acpi_get_devices() is an acpica function ?
Regards,
Hans
>>> ---
>>> v2: fix typo in previous commit -- my keyboard is eating letters
>>>
>>> drivers/gpu/drm/drm_privacy_screen_x86.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_privacy_screen_x86.c b/drivers/gpu/drm/drm_privacy_screen_x86.c
>>> index a2cafb294ca6..e7aa74ad0b24 100644
>>> --- a/drivers/gpu/drm/drm_privacy_screen_x86.c
>>> +++ b/drivers/gpu/drm/drm_privacy_screen_x86.c
>>> @@ -33,6 +33,9 @@ static bool __init detect_thinkpad_privacy_screen(void)
>>> unsigned long long output;
>>> acpi_status status;
>>>
>>> + if (acpi_disabled)
>>> + return false;
>>> +
>>> /* Get embedded-controller handle */
>>> status = acpi_get_devices("PNP0C09", acpi_set_handle, NULL, &ec_handle);
>>> if (ACPI_FAILURE(status) || !ec_handle)
>>
>
