linux-kernel - Re: [PATCH v6 7/7] auxdisplay: TM16xx: Add support for SPI-based controllers

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Message-ID: <aSSPKObizmpKiSpR@smile.fi.intel.com>
Date: Mon, 24 Nov 2025 19:00:24 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Jean-François Lessard <jefflessard3@...il.com>
Cc: Andy Shevchenko <andy@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v6 7/7] auxdisplay: TM16xx: Add support for SPI-based
 controllers

On Fri, Nov 21, 2025 at 09:59:07AM -0500, Jean-François Lessard wrote:
> Add support for TM16xx-compatible auxiliary display controllers connected
> via the SPI bus.
> 
> The implementation includes:
> - SPI driver registration and initialization
> - Probe/remove logic for SPI devices
> - Controller-specific handling and communication sequences
> - Integration with the TM16xx core driver for common functionality
> 
> This allows platforms using TM16xx or compatible controllers over SPI to be
> managed by the TM16xx driver infrastructure.

...

Seems like same/similar comments as per I2C glue driver are applicable here.
Please, address accordingly.

Additional comments below.

...

> +	tm16xx_for_each_key(display, row, col) {
> +		byte = col >> 1;

> +		bit = (2 - row) + ((col & 1) << 2);

If you do something like

		byte = col / 2;
		... = col % 2;

it may be optimised to a single assembly instruction on some architectures
by a compiler (and yes, I saw it in real life that `idiv` on x86 has been
chosen over other approaches by GCC).


> +		value = !!(codes[byte] & BIT(bit));

Seems unneeded

> +		tm16xx_set_key(display, row, col, value);

		tm16xx_set_key(display, row, col, codes[byte] & BIT(bit));


> +	}
> +
> +	return 0;
> +}

...

> +	tm16xx_set_key(display, 0, 0, !!(codes[0] & BIT(1)));
> +	tm16xx_set_key(display, 0, 1, !!(codes[0] & BIT(4)));
> +	tm16xx_set_key(display, 0, 2, !!(codes[1] & BIT(1)));
> +	tm16xx_set_key(display, 0, 3, !!(codes[1] & BIT(4)));
> +	tm16xx_set_key(display, 0, 4, !!(codes[2] & BIT(1)));

Do we really need !!() ?

-- 
With Best Regards,
Andy Shevchenko