linux-kernel - Re: [PATCH v7 4/5] nvmem: eeprom: at25: export FRAM serial num

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Message-ID: <YL4S2/hlfRwRM+Ug@kroah.com>
Date:   Mon, 7 Jun 2021 14:36:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jiri Prchal <jiri.prchal@...ignal.cz>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Christian Eggers <ceggers@...i.de>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v7 4/5] nvmem: eeprom: at25: export FRAM serial num

On Mon, Jun 07, 2021 at 02:26:39PM +0200, Jiri Prchal wrote:
> This exports serial number of FRAM in sysfs file named "sernum".
> Formatted in hex, each byte separated by space.
> Example:
> $ cat /sys/class/spi_master/spi0/spi0.0/sernum
> 0000a43644f2ae6c
> 
> Signed-off-by: Jiri Prchal <jiri.prchal@...ignal.cz>
> ---
> v2: no change here
> v3: resend and added more recipients
> v4: resend
> v5: reworked up on Greg comments: no spaces in string, sysfs done correctly
> v6: no change here
> v7: moved FM25_SN_LEN, static array, used sysfs_emit, DEVICE_ATTR_RO
> ---
>  drivers/misc/eeprom/at25.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
> index 3b7ffef1f0d7..a28dfd7e1798 100644
> --- a/drivers/misc/eeprom/at25.c
> +++ b/drivers/misc/eeprom/at25.c
> @@ -31,6 +31,7 @@
>   *   AT25M02, AT25128B
>   */
>  
> +#define	FM25_SN_LEN	8		/* serial number length */
>  struct at25_data {
>  	struct spi_device	*spi;
>  	struct mutex		lock;
> @@ -39,6 +40,7 @@ struct at25_data {
>  	struct nvmem_config	nvmem_config;
>  	struct nvmem_device	*nvmem;
>  	int has_sernum;
> +	u8 sernum[FM25_SN_LEN];
>  };
>  
>  #define	AT25_WREN	0x06		/* latch the write enable */
> @@ -172,6 +174,21 @@ static int fm25_aux_read(struct at25_data *at25, char *buf, uint8_t command,
>  	return status;
>  }
>  
> +static ssize_t sernum_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct at25_data *at25;
> +
> +	at25 = dev_get_drvdata(dev);
> +	return sysfs_emit(buf, "%016llx\n", *(unsigned long long *)at25->sernum);

That's a horrid hack, why not use the %*phN modifier?

Look in the printk-formats.rst file for help.

thanks,

greg k-h