linux-kernel - Re: [PATCH v3 1/8] platform/x86/intel/ifs: Reorganize driver data

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Date:   Mon, 13 Mar 2023 14:34:47 -0700
From:   "Joseph, Jithu" <jithu.joseph@...el.com>
To:     Hans de Goede <hdegoede@...hat.com>, <markgross@...nel.org>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
        <gregkh@...uxfoundation.org>, <rostedt@...dmis.org>,
        <ashok.raj@...el.com>, <tony.luck@...el.com>,
        <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <patches@...ts.linux.dev>,
        <ravi.v.shankar@...el.com>, <thiago.macieira@...el.com>,
        <athenas.jimenez.gonzalez@...el.com>, <sohil.mehta@...el.com>
Subject: Re: [PATCH v3 1/8] platform/x86/intel/ifs: Reorganize driver data



On 3/13/2023 7:46 AM, Hans de Goede wrote:
> Hi Jithu,
> 
> On 3/1/23 02:59, Jithu Joseph wrote:

>>  
>> +struct ifs_const_data {
>> +	int	integrity_cap_bit;
>> +	int	test_num;
>> +};
>> +
> 
> This is a description of the specific capabilties / bits of
> the IFS on e.g. Saphire Rapids, so please name this appropriately
> for example:
> 
> struct ifs_hw_caps  {
> 	int	integrity_cap_bit;
> 	int	test_num;
> };

This can be renamed to ifs_test_caps as it holds test specific fields.

...

> 
> You got this exactly the wrong way around, there should be a single
> 
> static const struct ifs_hw_caps saphire_rapids_caps = {
> 	.integrity_cap_bit = MSR_INTEGRITY_CAPS_PERIODIC_BIST_BIT,
> 	.test_num = 0,
> };
> 
> And then struct ifs_device { } should have a "const struct ifs_hw_caps *hw_caps"
> which gets initialized to point to &saphire_rapids_caps. So that your const
> data is actually const.
> 
> Where as since the r/w data's lifetime is couple to the misc-device lifetime
> there is no need to dynamically allocate it just keep that embedded, so that
> together you get:

Noted 

> 
> struct ifs_device {
> 	const struct ifs_hw_caps *hw_caps;
> 	struct ifs_data data;
> 	struct miscdevice misc;
> };
> 

The initialization portion, taking into account your suggestion above, translates to:

static const struct ifs_test_caps scan_test = {
	.integrity_cap_bit = MSR_INTEGRITY_CAPS_PERIODIC_BIST_BIT,
	.test_num = IFS_TYPE_SAF,
};

static const struct ifs_test_caps array_test = {
	.integrity_cap_bit = MSR_INTEGRITY_CAPS_ARRAY_BIST_BIT,
	.test_num = IFS_TYPE_ARRAY_BIST,
};

static struct ifs_device ifs_devices[] = {
	[IFS_TYPE_SAF] = {
		.test_caps = &scan_test,
		.misc = {
			.name = "intel_ifs_0",
			.minor = MISC_DYNAMIC_MINOR,
			.groups = plat_ifs_groups,
		},
	},
	[IFS_TYPE_ARRAY_BIST] = {
		.test_caps = &array_test,
		.misc = {
			.name = "intel_ifs_1",
			.minor = MISC_DYNAMIC_MINOR,
			.groups = plat_ifs_array_groups,
		},
	},
};

Jithu