linux-kernel - Re: [PATCH 2/4] hwmon: adc: rp1: Add Raspberry Pi's RP1 ADC driver

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Message-ID: <3f1295b0-b637-4fe0-b141-67f086960072@roeck-us.net>
Date: Thu, 25 Sep 2025 07:34:16 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Stefan Wahren <wahrenst@....net>
Cc: Stanimir Varbanov <svarbanov@...e.de>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
	Rob Herring <robh@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Saenz Julienne <nsaenz@...nel.org>,
	Andrea della Porta <andrea.porta@...e.com>,
	Phil Elwell <phil@...pberrypi.com>,
	Jonathan Bell <jonathan@...pberrypi.com>,
	Dave Stevenson <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH 2/4] hwmon: adc: rp1: Add Raspberry Pi's RP1 ADC driver

On Thu, Sep 25, 2025 at 07:26:10AM +0200, Stefan Wahren wrote:
> Hi Guenter,
> 
> Am 25.09.25 um 04:42 schrieb Guenter Roeck:
> > On Thu, Sep 25, 2025 at 03:04:14AM +0300, Stanimir Varbanov wrote:
> > > A five-input successive-approximation analogue-to-digital converter
> > > with 12-bit (effective number of 9.5 bits) resolution at 500kSPS.
> > > The ADC has four external inputs and one internal temperature sensor.
> > > 
> > > Signed-off-by: Phil Elwell <phil@...pberrypi.com>
> > > Signed-off-by: Jonathan Bell <jonathan@...pberrypi.com>
> > > Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> > I just realized that there is already a hwmon driver for
> > Rasperri Pi - drivers/hwmon/raspberrypi-hwmon.c.
> > 
> > Please add this code to that driver.
> could you please explain the reason for this?
> 
> Yes, both drivers are for Raspberry Pi boards, but they don't share any code
> base. The raspberrypi-hwmon uses a mailbox interfaces to get the sensor data
> and works for the board generation 1 - 4. This driver works completely
> differently ( MMIO ), doesn't depend on the mailbox interface and applies
> only for board generation 5. Actually I don't see a benefit of merging them.
> 
Ok. Please make sure to add this explanation to the patch description.

Guenter