linux-kernel - Re: [PATCH v7 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

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Message-ID: <5158fda4-6bf6-45b8-bbe0-8b469066d0ef@lunn.ch>
Date: Tue, 10 Feb 2026 18:48:16 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Shenwei Wang <shenwei.wang@....com>
Cc: Linus Walleij <linusw@...nel.org>,
	Bartosz Golaszewski <brgl@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Jonathan Corbet <corbet@....net>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, Peng Fan <peng.fan@....com>,
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-remoteproc@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, linux-imx@....com,
	arnaud.pouliquen@...s.st.com, Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH v7 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

> +#define GPIOS_PER_PORT		32

Maybe this should be from DT, using "ngpios". The Documentation says:

  Optionally, a GPIO controller may have a "ngpios" property. This
  property indicates the number of in-use slots of available slots for
  GPIOs. The typical example is something like this: the hardware
  register is 32 bits wide, but only 18 of the bits have a physical
  counterpart. The driver is generally written so that all 32 bits can
  be used, but the IP block is reused in a lot of designs, some using
  all 32 bits, some using 18 and some using 12. In this case, setting
  "ngpios = <18>;" informs the driver that only the first 18 GPIOs, at
  local offset 0 .. 17, are in use.

Just because your hardware has 32 does not mean every vendor does.

> +struct gpio_rpmsg_head {
> +	u8 id;		/* Message ID Code */
> +	u8 vendor;	/* Vendor ID number */
> +	u8 version;	/* Vendor-specific version number */
> +	u8 type;	/* Message type */
> +	u8 cmd;		/* Command code */
> +	u8 reserved[5];
> +} __packed;

I still think this should be a clean design from scratch, and you
modify your firmware.

This data structure is 10 bytes. Are these all needed for a generic
GPIO controller? version, type, command and one reserved byte seems
like enough, and it is then 4 bytes, so there is no need for __packed.

> +struct gpio_rpmsg_packet {
> +	struct gpio_rpmsg_head header;
> +	u8 pin_idx;
> +	u8 port_idx;
> +	union {
> +		u8 event;
> +		u8 retcode;
> +		u8 value;
> +	} out;
> +	union {
> +		u8 wakeup;
> +		u8 value;
> +	} in;
> +} __packed __aligned(8);

This then becomes 8 bytes, so there is no need for __packed or
__aligned(8).

I don't want to force this, it is something i think which should be
discussed. Do we adopt your design, which is not so nice, but at least
has one working implementation, or do we do a clean design?

> +static int gpio_send_message(struct rpmsg_gpio_port *port,
> +			     struct gpio_rpmsg_packet *msg,
> +			     bool sync)
> +{
> +	struct gpio_rpmsg_info *info = &port->info;
> +	int err;
> +
> +	reinit_completion(&info->cmd_complete);
> +	err = rpmsg_send(info->rpdev->ept, msg, sizeof(struct gpio_rpmsg_packet));
> +	if (err) {
> +		dev_err(&info->rpdev->dev, "rpmsg_send failed: %d\n", err);
> +		return err;
> +	}
> +
> +	if (sync) {
> +		err = wait_for_completion_timeout(&info->cmd_complete,
> +						  msecs_to_jiffies(RPMSG_TIMEOUT));
> +		if (!err) {
> +			dev_err(&info->rpdev->dev, "rpmsg_send timeout!\n");
> +			return -ETIMEDOUT;
> +		}

I _think_ you need to handle negative values of err. It looks like
do_wait_for_common() can return -ERESTARTSYS;

> +static struct gpio_rpmsg_packet *gpio_setup_msg_header(struct rpmsg_gpio_port *port,
> +						       unsigned int offset,
> +						       u8 cmd)
> +{
> +	struct gpio_rpmsg_packet *msg = &port->gpio_pins[offset].msg;
> +
> +	memset(msg, 0, sizeof(struct gpio_rpmsg_packet));
> +	msg->header.id = RPMSG_GPIO_ID;
> +	msg->header.vendor = RPMSG_VENDOR;
> +	msg->header.version = RPMSG_VERSION;
> +	msg->header.type = GPIO_RPMSG_SETUP;
> +	msg->header.cmd = cmd;
> +	msg->pin_idx = offset;
> +	msg->port_idx = port->idx;

Why is a function called gpio_setup_msg_header() setting things
outside of the header?

> +static int rpmsg_gpio_get(struct gpio_chip *gc, unsigned int gpio)
> +{
> +	struct rpmsg_gpio_port *port = gpiochip_get_data(gc);
> +	struct gpio_rpmsg_packet *msg;
> +	int ret;
> +
> +	guard(mutex)(&port->info.lock);
> +
> +	msg = gpio_setup_msg_header(port, gpio, GPIO_RPMSG_INPUT_GET);
> +
> +	ret = gpio_send_message(port, msg, true);

If gpio_setup_msg_header() does what it sounds like it should do, what
is setting up the message body before you send the message?

	Andrew