linux-hardening - Re: [PATCH v3 net-next 5/8] mfd: zl3073x: Add functions to work with register mailboxes

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Message-ID: <20250417161354.GF372032@google.com>
Date: Thu, 17 Apr 2025 17:13:54 +0100
From: Lee Jones <lee@...nel.org>
To: Ivan Vecera <ivecera@...hat.com>
Cc: netdev@...r.kernel.org, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
	Jiri Pirko <jiri@...nulli.us>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Prathosh Satish <Prathosh.Satish@...rochip.com>,
	Kees Cook <kees@...nel.org>, Andy Shevchenko <andy@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Schmidt <mschmidt@...hat.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3 net-next 5/8] mfd: zl3073x: Add functions to work with
 register mailboxes

On Wed, 16 Apr 2025, Ivan Vecera wrote:

> Registers present in page 10 and higher are called mailbox type
> registers. Each page represents a mailbox and is used to read and write
> configuration of particular object (dpll, output, reference & synth).
> 
> The mailbox page contains mask register that is used to select an index of
> requested object to work with and semaphore register to indicate what
> operation is requested.
> 
> The rest of registers in the particular register page are latch
> registers that are filled by the firmware during read operation or by
> the driver prior write operation.
> 
> For read operation the driver...
> 1) ... updates the mailbox mask register with index of particular object
> 2) ... sets the mailbox semaphore register read bit
> 3) ... waits for the semaphore register read bit to be cleared by FW
> 4) ... reads the configuration from latch registers
> 
> For write operation the driver...
> 1) ... writes the requested configuration to latch registers
> 2) ... sets the mailbox mask register for the DPLL to be updated
> 3) ... sets the mailbox semaphore register bit for the write operation
> 4) ... waits for the semaphore register bit to be cleared by FW
> 
> Add functions to read and write mailboxes for all supported object types.
> 
> All these functions as well as functions accessing mailbox latch registers
> (zl3073x_mb_* functions) have to be called with zl3073x_dev->mailbox_lock
> held and a caller is responsible to take this lock.
> 
> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
> v1->v3:
> * dropped ZL3073X_MB_OP macro usage
> ---
>  drivers/mfd/zl3073x-core.c       | 232 +++++++++++++++++++++++
>  include/linux/mfd/zl3073x.h      |  12 ++
>  include/linux/mfd/zl3073x_regs.h | 304 +++++++++++++++++++++++++++++++
>  3 files changed, 548 insertions(+)

> +/*
> + * Mailbox operations
> + */
> +int zl3073x_mb_dpll_read(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_dpll_write(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_output_read(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_output_write(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_ref_read(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_ref_write(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_synth_read(struct zl3073x_dev *zldev, u8 index);
> +int zl3073x_mb_synth_write(struct zl3073x_dev *zldev, u8 index);

Why aren't these being placed into drivers/mailbox?

-- 
Lee Jones [李琼斯]