linux-kernel - Re: [PATCH 01/11] spi: spi-mem: Extend the SPI mem interface to set a custom memory name

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Date:   Wed, 30 May 2018 16:32:20 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Frieder Schrempf <frieder.schrempf@...eet.de>
Cc:     linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
        dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, richard@....at, miquel.raynal@...tlin.com,
        broonie@...nel.org, david.wolfe@....com, fabio.estevam@....com,
        prabhakar.kushwaha@....com, yogeshnarayan.gaur@....com,
        han.xu@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] spi: spi-mem: Extend the SPI mem interface to set
 a custom memory name

Hi Frieder,

On Wed, 30 May 2018 15:14:30 +0200
Frieder Schrempf <frieder.schrempf@...eet.de> wrote:

> When porting (Q)SPI controller drivers from the MTD layer to the SPI
> layer, the naming scheme for the memory devices changes. To be able
> to keep compatibility with the old drivers naming scheme, a function
> is added to the SPI mem interface to let controller drivers set a
> custom name for the memory.
> 
> Example for the FSL QSPI driver:
> 
> Name with the old driver: 21e0000.qspi,
> or with multiple devices: 21e0000.qspi-0, 21e0000.qspi-1, ...
> 
> Name with the new driver without spi_mem_get_name: spi4.0
> 
> Signed-off-by: Frieder Schrempf <frieder.schrempf@...eet.de>
> ---
>  drivers/spi/spi-mem.c       | 25 +++++++++++++++++++++++++
>  include/linux/spi/spi-mem.h |  3 +++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 990770d..5e9af47 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -311,6 +311,31 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
>  EXPORT_SYMBOL_GPL(spi_mem_exec_op);
>  
>  /**
> + * spi_mem_get_name() - Let drivers using the SPI mem interface specify a
> + *			custom name for the memory to avoid compatibility
> + *			issues with ported drivers.
> + * @mem: the SPI memory
> + *
> + * When porting (Q)SPI controller drivers from the MTD layer to the SPI
> + * layer, the naming scheme for the memory devices changes. To be able to
> + * keep compatibility with the old drivers naming scheme, this function can
> + * be used to get a custom name from the controller driver.
> + * If no custom name is available, the name of the SPI device is returned.
> + *
> + * Return: a char array that contains the name for the flash memory
> + */
> +const char *spi_mem_get_name(struct spi_mem *mem)
> +{
> +	struct spi_controller *ctlr = mem->spi->controller;
> +
> +	if (ctlr->mem_ops && ctlr->mem_ops->get_name)
> +		return ctlr->mem_ops->get_name(mem);

Looks like your implementation of ->get_name() in the fsl driver is
allocating a new string each time it's called. I guess other
implementations might be forced to do the same, so maybe it's better to
add a ->name field to struct spi_mem and only call ->get_name() once
when the device is probed. Then spi_mem_get_name() can just be
implemented like this:

const char *spi_mem_get_name(struct spi_mem *mem)
{
	return mem->name;
}

Regards,

Boris

> +
> +	return dev_name(&mem->spi->dev);
> +}
> +EXPORT_SYMBOL_GPL(spi_mem_get_name);
> +
> +/**
>   * spi_mem_adjust_op_size() - Adjust the data size of a SPI mem operation to
>   *			      match controller limitations
>   * @mem: the SPI memory
> diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> index 4fa34a2..f1912d3 100644
> --- a/include/linux/spi/spi-mem.h
> +++ b/include/linux/spi/spi-mem.h
> @@ -178,6 +178,7 @@ struct spi_controller_mem_ops {
>  			    const struct spi_mem_op *op);
>  	int (*exec_op)(struct spi_mem *mem,
>  		       const struct spi_mem_op *op);
> +	const char *(*get_name)(struct spi_mem *mem);
>  };
>  
>  /**
> @@ -236,6 +237,8 @@ bool spi_mem_supports_op(struct spi_mem *mem,
>  int spi_mem_exec_op(struct spi_mem *mem,
>  		    const struct spi_mem_op *op);
>  
> +const char *spi_mem_get_name(struct spi_mem *mem);
> +
>  int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
>  				       struct module *owner);
>