linux-kernel - Re: [PATCH 1/6] platform/x86: firmware_attributes

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Message-ID: <f4783864-1bbe-48ea-9a2e-2709c94c519c@gmx.de>
Date: Sat, 4 Jan 2025 08:20:48 +0100
From: Armin Wolf <W_Armin@....de>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Hans de Goede <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Mark Pearson <markpearson@...ovo.com>, Jorge Lopez <jorge.lopez2@...com>,
 Prasanth Ksr <prasanth.ksr@...l.com>, Joshua Grisham
 <josh@...huagrisham.com>, platform-driver-x86@...r.kernel.org,
 linux-kernel@...r.kernel.org, Dell.Client.Kernel@...l.com
Subject: Re: [PATCH 1/6] platform/x86: firmware_attributes_class: Move include
 linux/device/class.h

Am 04.01.25 um 08:06 schrieb Thomas Weißschuh:

> Hi,
>
> On 2025-01-04 07:55:15+0100, Armin Wolf wrote:
>> Am 04.01.25 um 00:05 schrieb Thomas Weißschuh:
>>
>>> The header firmware_attributes_class.h uses 'struct class'. It should
>>> also include the necessary dependency header.
>> i like this patch series, but i would prefer that we do not expose the raw class through the header.
>>
>> Looking at the callers of fw_attributes_class_get(), everywhere the class value is used only to call:
>>
>> 	device_create(fw_attr_class, NULL, MKDEV(0, 0), NULL, "%s", <driver name>);
>>
>> I suggest that we introduce two new functions for that:
>>
>> 	struct device *firmware_attributes_device_register(struct device *parent, const char *name);
>>
>> 	void firmware_attributes_device_unregister(struct device *dev);
>>
>> This would have three major benefits:
>>
>> - the raw class can be made internal
>> - reduced code size
>> - drivers would stop copying the flawed use of device_destroy()
>>
>> Regarding the use of device_destroy(): this is actually an error since device_destroy() cannot be
>> reliably used when devt is not unique. Since all those drivers are setting devt to MKDEV(0, 0) this
>> could result in a kernel panic should multiple firmware-attribute class devices exist at the same time.
>>
>> What do you think?
> Completely agree. This is exactly what the "further improvements"
> mentioned in the cover letter do.
> And also add devm_firmware_attributes_device_register() and a custom
> sysfs attribute type that makes the driver code much simplerr.
>
> But this will be some more work. Also the conversions of the drivers
> will be harder and take longer, so we can't drop the raw exposed class
> as easily and have to keep the "legacy" interface for a bit.

Fair point. In this case the current approach should be fine.

>> Thanks,
>> Armin Wolf
>>
>>> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
>>> ---
>>>    drivers/platform/x86/firmware_attributes_class.c | 1 -
>>>    drivers/platform/x86/firmware_attributes_class.h | 2 ++
>>>    2 files changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
>>> index 182a07d8ae3dfa8925bb5b71a43d0219c3cf0fa0..cbc56e5db59283ba99ac0b915ac5fb2432afbdc9 100644
>>> --- a/drivers/platform/x86/firmware_attributes_class.c
>>> +++ b/drivers/platform/x86/firmware_attributes_class.c
>>> @@ -3,7 +3,6 @@
>>>    /* Firmware attributes class helper module */
>>>
>>>    #include <linux/mutex.h>
>>> -#include <linux/device/class.h>
>>>    #include <linux/module.h>
>>>    #include "firmware_attributes_class.h"
>>>
>>> diff --git a/drivers/platform/x86/firmware_attributes_class.h b/drivers/platform/x86/firmware_attributes_class.h
>>> index 363c75f1ac1b89df879a8689b070e6b11d3bb7fd..8e0f47cfdf92eb4dc8722b7d8371916af0d84efa 100644
>>> --- a/drivers/platform/x86/firmware_attributes_class.h
>>> +++ b/drivers/platform/x86/firmware_attributes_class.h
>>> @@ -5,6 +5,8 @@
>>>    #ifndef FW_ATTR_CLASS_H
>>>    #define FW_ATTR_CLASS_H
>>>
>>> +#include <linux/device/class.h>

I think it would make more sense to not include the complete class header and instead only
define "struct class;" inside firmware_attributes_class.h.

Thanks,
Armin Wolf

>>> +
>>>    int fw_attributes_class_get(const struct class **fw_attr_class);
>>>    int fw_attributes_class_put(void);
>>>
>>>