linux-kernel - Re: [RFC PATCH] nvmem: core: add sysfs cell write support

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Date: Fri, 16 Feb 2024 11:07:50 +0100
From: Marco Felsch <m.felsch@...gutronix.de>
To: Michael Walle <michael@...le.cc>
Cc: srinivas.kandagatla@...aro.org, gregkh@...uxfoundation.org,
	miquel.raynal@...tlin.com, rafal@...ecki.pl,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [RFC PATCH] nvmem: core: add sysfs cell write support

Hi Michael,

On 24-02-16, Michael Walle wrote:
> Hi,
> 
> On Thu Feb 15, 2024 at 10:14 PM CET, Marco Felsch wrote:
> > @@ -432,6 +466,7 @@ static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
> >  	struct bin_attribute **cells_attrs, *attrs;
> >  	struct nvmem_cell_entry *entry;
> >  	unsigned int ncells = 0, i = 0;
> > +	umode_t mode;
> >  	int ret = 0;
> >  
> >  	mutex_lock(&nvmem_mutex);
> > @@ -456,15 +491,18 @@ static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
> >  		goto unlock_mutex;
> >  	}
> >  
> > +	mode = nvmem_bin_attr_get_umode(nvmem);
> > +
> >  	/* Initialize each attribute to take the name and size of the cell */
> >  	list_for_each_entry(entry, &nvmem->cells, node) {
> >  		sysfs_bin_attr_init(&attrs[i]);
> >  		attrs[i].attr.name = devm_kasprintf(&nvmem->dev, GFP_KERNEL,
> >  						    "%s@%x", entry->name,
> >  						    entry->offset);
> > -		attrs[i].attr.mode = 0444;
> 
> cells are not writable if there is a read post process hook, see
> __nvmem_cell_entry_write().
> 
> if (entry->read_post_processing)
> 	mode &= ~0222;

good point, thanks for the hint :) I will add this and send a non-rfc
version if write-support is something you would like to have.

Regards,
  Marco

> 
> -michael