Re: [PATCH] eeprom: at24: verify that chip is accessible during probe

[Marco Felsch <m.felsch@pengutronix.de>]

On 26-02-23, Sascha Hauer wrote:
> On Wed, Feb 18, 2026 at 01:42:48PM +0100, Marco Felsch wrote:
> > Perform a basic sanity check to verify that the EEPROM is actually
> > accessible by reading 1-byte. Linux does the same sanity check for all
> > non-ACPI platforms.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> > ---
> >  drivers/eeprom/at24.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/eeprom/at24.c b/drivers/eeprom/at24.c
> > index 06a2a4b22697..a08d42fe3e14 100644
> > --- a/drivers/eeprom/at24.c
> > +++ b/drivers/eeprom/at24.c
> > @@ -373,6 +373,7 @@ static int at24_probe(struct device *dev)
> >  	unsigned i, num_addresses;
> >  	const char *devname;
> >  	const char *alias;
> > +	u8 test_byte;
> >  
> >  	if (dev->platform_data) {
> >  		chip = *(struct at24_platform_data *)dev->platform_data;
> > @@ -487,6 +488,12 @@ static int at24_probe(struct device *dev)
> >  	at24->nvmem_config.size = chip.byte_len;
> >  	at24->nvmem_config.id = devid;
> >  
> > +	/* Perform a one-byte test read to verify that the chip is functional */
> > +	if (at24_read(at24, &test_byte, 0, 1) != 1) {
> > +		err = -ENODEV;
> 
> a return of -ENODEV from driver probe doesn't print an error. Is that
> what we want here?

That's a good point, quickly checked the Linux implementation which
doesn't print an error too. However, you're right and we should print a
dev_err() or so here. Is this something you may add while applying or
shall I send a new v2?

Regards,
  Marco


> 
> Sascha
> 
> > +		goto err_devfs_create;
> > +	}
> > +
> >  	at24->nvmem = nvmem_register(&at24->nvmem_config);
> >  	err = PTR_ERR_OR_ZERO(at24->nvmem);
> >  	if (err)
> > -- 
> > 2.47.3
> > 
> > 
> > 
> 
> -- 
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