linux-kernel - Re: [PATCH v3 04/11] dmaengine: Add selfirq callback registration API

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Message-ID: <aYOF_JNYZF9IFUCr@lizhi-Precision-Tower-5810>
Date: Wed, 4 Feb 2026 12:46:36 -0500
From: Frank Li <Frank.li@....com>
To: Koichiro Den <den@...inux.co.jp>
Cc: vkoul@...nel.org, mani@...nel.org, jingoohan1@...il.com,
	lpieralisi@...nel.org, kwilczynski@...nel.org, robh@...nel.org,
	bhelgaas@...gle.com, dmaengine@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 04/11] dmaengine: Add selfirq callback registration API

On Wed, Feb 04, 2026 at 11:54:32PM +0900, Koichiro Den wrote:
> Some DMA controllers can generate an interrupt by software writing to a
> register, without updating the normal interrupt status bits. This can be
> used as a doorbell mechanism when the DMA engine is remotely programmed,
> or for self-tests.
>
> Add an optional per-DMA-device API to register/unregister callbacks for
> such "selfirq" events. Providers may invoke these callbacks from their
> interrupt handler when they detect an emulated interrupt.
>
> Callbacks are invoked in hardirq context and must not sleep.

Is it possible register shared irq handle with the same channel's irq
number?

Frank

>
> Signed-off-by: Koichiro Den <den@...inux.co.jp>
> ---
>  include/linux/dmaengine.h | 70 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 71bc2674567f..9c6194e8bfe1 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -785,6 +785,17 @@ struct dma_filter {
>  	const struct dma_slave_map *map;
>  };
>
> +/**
> + * dma_selfirq_fn - callback for emulated/self IRQ events
> + * @dev: DMA device invoking the callback
> + * @data: opaque pointer provided at registration time
> + *
> + * Providers may invoke this callback from their interrupt handler when an
> + * emulated interrupt ("selfirq") might have occurred. The callback runs in
> + * hardirq context and must not sleep.
> + */
> +typedef void (*dma_selfirq_fn)(struct dma_device *dev, void *data);
> +
>  /**
>   * struct dma_device - info on the entity supplying DMA services
>   * @ref: reference is taken and put every time a channel is allocated or freed
> @@ -853,6 +864,10 @@ struct dma_filter {
>   *	or an error code
>   * @device_synchronize: Synchronizes the termination of a transfers to the
>   *  current context.
> + * @device_register_selfirq: optional callback registration for
> + *	emulated/self IRQ events
> + * @device_unregister_selfirq: unregister previously registered selfirq
> + *	callback
>   * @device_tx_status: poll for transaction completion, the optional
>   *	txstate parameter can be supplied with a pointer to get a
>   *	struct with auxiliary transfer status information, otherwise the call
> @@ -951,6 +966,11 @@ struct dma_device {
>  	int (*device_terminate_all)(struct dma_chan *chan);
>  	void (*device_synchronize)(struct dma_chan *chan);
>
> +	int (*device_register_selfirq)(struct dma_device *dev,
> +				       dma_selfirq_fn fn, void *data);
> +	void (*device_unregister_selfirq)(struct dma_device *dev,
> +					  dma_selfirq_fn fn, void *data);
> +
>  	enum dma_status (*device_tx_status)(struct dma_chan *chan,
>  					    dma_cookie_t cookie,
>  					    struct dma_tx_state *txstate);
> @@ -1197,6 +1217,56 @@ static inline void dmaengine_synchronize(struct dma_chan *chan)
>  		chan->device->device_synchronize(chan);
>  }
>
> +/**
> + * dmaengine_register_selfirq() - Register a callback for emulated/self IRQ
> + *                                events
> + * @dev: DMA device
> + * @fn: callback invoked from the provider's IRQ handler
> + * @data: opaque callback data
> + *
> + * Some DMA controllers can raise an interrupt by software writing to a
> + * register without updating normal status bits. Providers may call
> + * registered callbacks from their interrupt handler when such events may
> + * have occurred.
> + * Callbacks are invoked in hardirq context and must not sleep.
> + *
> + * Return: 0 on success, -EOPNOTSUPP if unsupported, -EINVAL on bad args,
> + * or provider-specific -errno.
> + */
> +static inline int dmaengine_register_selfirq(struct dma_device *dev,
> +					     dma_selfirq_fn fn, void *data)
> +{
> +	if (!dev || !fn)
> +		return -EINVAL;
> +	if (!dev->device_register_selfirq)
> +		return -EOPNOTSUPP;
> +
> +	return dev->device_register_selfirq(dev, fn, data);
> +}
> +
> +/**
> + * dmaengine_unregister_selfirq() - Unregister a previously registered
> + *                                  selfirq callback
> + * @dev: DMA device
> + * @fn: callback pointer used at registration time
> + * @data: opaque pointer used at registration time
> + *
> + * Unregister a callback previously registered via
> + * dmaengine_register_selfirq(). Providers may synchronize against
> + * in-flight callbacks, therefore this function may sleep and must not be
> + * called from atomic context.
> + */
> +static inline void dmaengine_unregister_selfirq(struct dma_device *dev,
> +						dma_selfirq_fn fn, void *data)
> +{
> +	if (!dev || !fn)
> +		return;
> +	if (!dev->device_unregister_selfirq)
> +		return;
> +
> +	dev->device_unregister_selfirq(dev, fn, data);
> +}
> +
>  /**
>   * dmaengine_terminate_sync() - Terminate all active DMA transfers
>   * @chan: The channel for which to terminate the transfers
> --
> 2.51.0
>