Re: [PATCH RFC v3 2/9] spi: add basic support for SPI offloading

[David Lechner]

On 7/27/24 8:15 AM, Jonathan Cameron wrote:
> On Mon, 22 Jul 2024 16:57:09 -0500
> David Lechner <dlechner@xxxxxxxxxxxx> wrote:
> 


>> +/**
>> + * spi_offload_prepare - prepare offload hardware for a transfer
>> + * @spi:	The spi device to use for the transfers.
>> + * @id:		Function ID if SPI device uses more than one offload or NULL.
>> + * @msg:	The SPI message to use for the offload operation.
>> + *
>> + * Requests an offload instance with the specified ID and programs it with the
>> + * provided message.
>> + *
>> + * The message must not be pre-optimized (do not call spi_optimize_message() on
>> + * the message).
>> + *
>> + * Calls must be balanced with spi_offload_unprepare().
>> + *
>> + * Return: 0 on success, else a negative error code.
>> + */
>> +int spi_offload_prepare(struct spi_device *spi, const char *id,
>> +			struct spi_message *msg)
>> +{
>> +	struct spi_controller *ctlr = spi->controller;
>> +	int ret;
>> +
>> +	if (!ctlr->offload_ops)
>> +		return -EOPNOTSUPP;
>> +
>> +	msg->offload = true;
> I'd set this later perhaps as...

If we move it, then we would have to create a new function
to call instead of spi_optimize_message() so that the controller
driver can know that this is an offload message and not a
regular message since they will need to be handled differently
during the optimization phase.

>> +
>> +	ret = spi_optimize_message(spi, msg);
>> +	if (ret)
> 
> It otherwise needs clearing here so it doesn't have side
> effects if an error occurs.
> 
>> +		return ret;
>> +
>> +	mutex_lock(&ctlr->io_mutex);
>> +	ret = ctlr->offload_ops->prepare(spi, id, msg);
>> +	mutex_unlock(&ctlr->io_mutex);
>> +
>> +	if (ret) {
>> +		spi_unoptimize_message(msg);
>> +		msg->offload = false;
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(spi_offload_prepare);
>