linux-kernel - Re: [PATCH v3 8/8] misc: amd-sbi: Add document for AMD SB IOCTL description

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Message-ID: <2024081412-snowless-judgingly-ce90@gregkh>
Date: Wed, 14 Aug 2024 12:33:32 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Akshay Gupta <akshay.gupta@....com>
Cc: linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux@...ck-us.net, arnd@...db.de, naveenkrishna.chatradhi@....com
Subject: Re: [PATCH v3 8/8] misc: amd-sbi: Add document for AMD SB IOCTL
 description

On Wed, Aug 14, 2024 at 09:59:53AM +0000, Akshay Gupta wrote:
> +The following IOCTL is defined:
> +
> +``#define SB_BASE_IOCTL_NR      0xF9``
> +``#define SBRMI_IOCTL_CMD          _IOWR(SB_BASE_IOCTL_NR, 0, struct apml_message)``

You only have 1 ioctl, so why are you saying that you are reserving
0-1F?


> +Data structure::
> +	struct apml_message {
> +		/* message ids:
> +		 * Mailbox Messages:	0x0 ... 0x999
> +		 * APML_CPUID:		0x1000
> +		 * APML_MCA_MSR:	0x1001
> +		 * APML_REG:		0x1002
> +		 */
> +		__u32 cmd;
> +		/*
> +		 * 8 bit data for reg read,
> +		 * 32 bit data in case of mailbox,
> +		 * up to 64 bit in case of cpuid and mca msr
> +		 */
> +		union {
> +			__u64 cpu_msr_out;
> +			__u32 mb_out[2];
> +			__u8 reg_out[8];
> +		} data_out;
> +		/*
> +		 * [0]...[3] mailbox 32bit input
> +		 *	     cpuid & mca msr,
> +		 *	     rmi rd/wr: reg_offset
> +		 * [4][5] cpuid & mca msr: thread
> +		 * [4] rmi reg wr: value
> +		 * [6] cpuid: ext function & read eax/ebx or ecx/edx
> +		 *	[7:0] -> bits [7:4] -> ext function &
> +		 *	bit [0] read eax/ebx or ecx/edx
> +		 * [7] read/write functionality
> +		 */
> +		union {
> +			__u64 cpu_msr_in;
> +			__u32 mb_in[2];
> +			__u8 reg_in[8];
> +		} data_in;
> +		/*
> +		 * Status code is returned in case of CPUID/MCA access
> +		 * Error code is returned in case of soft mailbox
> +		 */
> +		__u32 fw_ret_code;
> +	} __attribute__((packed));

This does not need to be here, pull it directly from the .h file using
kernel doc formatting please.

> +The ioctl would return a non-zero on failure; user can read errno to see
> +what happened.

That's not how the ioctl syscall works :(

> The transaction returns 0 on success.
> +
> +User space C-APIs are made available by linking against the esmi_oob_library,
> +which is provided by the E-SMS project https://www.amd.com/en/developer/e-sms.html.
> +Link: https://github.com/amd/esmi_oob_library

What is this last line for?

thanks,

greg k-h