linux-kernel - Re: [PATCH] PCI: hotplug: Add extension driver for Ampere Altra hotplug LED control

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Date:   Thu, 28 Sep 2023 14:02:07 -0700
From:   D Scott Phillips <scott@...amperecomputing.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org,
        Darren Hart <darren@...amperecomputing.com>,
        patches@...erecomputing.com
Subject: Re: [PATCH] PCI: hotplug: Add extension driver for Ampere Altra
 hotplug LED control

Bjorn Helgaas <helgaas@...nel.org> writes:

> On Wed, Sep 27, 2023 at 01:23:47PM -0700, D Scott Phillips wrote:
>> On Ampere Altra, PCIe hotplug is handled through ACPI. A side interface is
>> also present to request system firmware control of attention LEDs. Add an
>> ACPI PCI Hotplug companion driver to support attention LED control.
>> 
>> Signed-off-by: D Scott Phillips <scott@...amperecomputing.com>
>> ---
>>  drivers/pci/hotplug/Kconfig                |  13 ++
>>  drivers/pci/hotplug/Makefile               |   3 +-
>>  drivers/pci/hotplug/acpiphp_ampere_altra.c | 141 +++++++++++++++++++++
>>  3 files changed, 156 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/pci/hotplug/acpiphp_ampere_altra.c
>> 
>> diff --git a/drivers/pci/hotplug/Kconfig b/drivers/pci/hotplug/Kconfig
>> index 48113b210cf93..9fde600a9ad3e 100644
>> --- a/drivers/pci/hotplug/Kconfig
>> +++ b/drivers/pci/hotplug/Kconfig
>> @@ -61,6 +61,19 @@ config HOTPLUG_PCI_ACPI
>>  
>>  	  When in doubt, say N.
>>  
>> +config HOTPLUG_PCI_ACPI_AMPERE_ALTRA
>> +	tristate "ACPI PCI Hotplug driver Ampere Altra extensions"
>> +	depends on HOTPLUG_PCI_ACPI
>> +	depends on HAVE_ARM_SMCCC_DISCOVERY
>> +	depends on m
>
> Why is this restricted to being a module?  It's not unprecedented, but
> unless this only works as a module for some reason, I would leave that
> choice up to the user.

I did that because acpiphp_register_attention() wouldn't register the
handler unless it was built as a module. Maybe better would be this
change first:

--- a/drivers/pci/hotplug/acpiphp_core.c
+++ b/drivers/pci/hotplug/acpiphp_core.c
@@ -78,8 +78,7 @@ int acpiphp_register_attention(struct acpiphp_attention_info *info)
 {
 	int retval = -EINVAL;
 
-	if (info && info->owner && info->set_attn &&
-			info->get_attn && !attention_info) {
+	if (info && info->set_attn && info->get_attn && !attention_info) {
 		retval = 0;
 		attention_info = info;
 	}