Re: [PATCH 5/7] ACPI: scan: Add support for deferring adding devices to the second scan phase based on the _DEP list

Rafael J. Wysocki
2020-11-23T13:18:06Z

On Sat, Nov 21, 2020 at 9:31 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> The current solution, of deferring adding of some devices because they
> need access during the OpRegions of other devices while they are added,
> is not very generic.
>
> And support for making the decision to defer adding a device based on
> its _DEP list, instead of the device's HID being in a fixed list of HIDs
> to defer, which should be a more generic way to deal with this.

Thanks a lot for working on this!

I'll have a more thorough look at the series later this week, stay tuned.

> Since this is likely to cause issues on some hardware, this new method will
> only be used if the new acpi.defer_scan_based_on_dep kernel commandline
> option is set to 1.

However, I already can say that I don't like the new command line option.

> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> drivers/acpi/scan.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 407c8536568b..9927036bfe77 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -31,6 +31,11 @@ extern struct acpi_device *acpi_root;
>
> #define INVALID_ACPI_HANDLE ((acpi_handle)empty_zero_page)
>
> +static int defer_scan_based_on_dep = -1;
> +module_param(defer_scan_based_on_dep, int, 0444);
> +MODULE_PARM_DESC(defer_scan_based_on_dep,
> + "Use new scan-scheme deferring addition of devices with non empty _DEP list (-1=auto, 0=no, 1=yes)");
> +
> static const char *dummy_hid = "device";
>
> static LIST_HEAD(acpi_dep_list);
> @@ -1657,11 +1662,45 @@ void acpi_device_add_finalize(struct acpi_device *device)
>
> static bool acpi_should_defer_add(acpi_handle handle, struct acpi_device_info *info)
> {
> + struct acpi_handle_list dep_devices;
> + acpi_status status;
> + int i;
> +
> if (!acpi_check_defer_add || !info)
> return false;
>
> - if (acpi_info_matches_hids(info, acpi_defer_add_hids))
> + if (!defer_scan_based_on_dep)
> + return acpi_info_matches_hids(info, acpi_defer_add_hids);
> +
> + /*
> + * We check for _ADR here to avoid deferring the adding of the following:
> + * 1. PCI devices
> + * 2. ACPI nodes describing USB ports
> + * Note checking for _ADR catches more then just these cases...

s/then/than/

> + */
> + if (info->valid & ACPI_VALID_ADR)
> + return false;
> +
> + status = acpi_evaluate_reference(handle, "_DEP", NULL, &dep_devices);
> + if (ACPI_FAILURE(status))
> + return false;
> +
> + for (i = 0; i < dep_devices.count; i++) {
> + struct acpi_device_info *dep_info;
> + bool ignore;
> +
> + status = acpi_get_object_info(dep_devices.handles[i], &dep_info);
> + if (ACPI_FAILURE(status))
> + continue;
> +
> + ignore = acpi_info_matches_hids(dep_info, acpi_ignore_dep_hids);
> + kfree(dep_info);
> +
> + if (ignore)
> + continue;
> +
> return true;
> + }
>
> return false;
> }
> @@ -2251,6 +2290,10 @@ int __init acpi_scan_init(void)
> struct acpi_table_stao *stao_ptr;
> struct acpi_deferred_dev *deferred_dev, *tmp;
>
> + /* Currently no devices are known which need _dep based scan deferral */
> + if (defer_scan_based_on_dep == -1)
> + defer_scan_based_on_dep = 0;
> +
> acpi_pci_root_init();
> acpi_pci_link_init();
> acpi_processor_init();
> --
> 2.28.0
>