linux-kernel - Re: [PATCH v12 7/7] nvmem: core: Expose cells through sysfs

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Message-ID: <20231011091524.0c9ecc55@xps-13>
Date:   Wed, 11 Oct 2023 09:15:24 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Walle <michael@...le.cc>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Robert Marko <robert.marko@...tura.hr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Randy Dunlap <rdunlap@...radead.org>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Daniel Golle <daniel@...rotopia.org>
Subject: Re: [PATCH v12 7/7] nvmem: core: Expose cells through sysfs

Hi Srinivas,

> > +{
> > +	struct bin_attribute **cells_attrs, *attrs;
> > +	struct nvmem_cell_entry *entry;
> > +	unsigned int ncells = 0, i = 0;
> > +	int ret = 0;
> > +
> > +	mutex_lock(&nvmem_mutex);
> > +
> > +	if (list_empty(&nvmem->cells) || nvmem->sysfs_cells_populated) {
> > +		nvmem_cells_group.bin_attrs = NULL;
> > +		goto unlock_mutex;
> > +	}
> > +
> > +	/* Allocate an array of attributes with a sentinel */
> > +	ncells = list_count_nodes(&nvmem->cells);
> > +	cells_attrs = devm_kcalloc(&nvmem->dev, ncells + 1,
> > +				   sizeof(struct bin_attribute *), GFP_KERNEL);
> > +	if (!cells_attrs) {
> > +		ret = -ENOMEM;
> > +		goto unlock_mutex;
> > +	}
> > +
> > +	attrs = devm_kcalloc(&nvmem->dev, ncells, sizeof(struct bin_attribute), GFP_KERNEL);
> > +	if (!attrs) {
> > +		ret = -ENOMEM;
> > +		goto unlock_mutex;
> > +	}
> > +
> > +	/* 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;
> > +		attrs[i].size = entry->bytes;
> > +		attrs[i].read = &nvmem_cell_attr_read;
> > +		attrs[i].private = entry;
> > +		if (!attrs[i].attr.name) {
> > +			ret = -ENOMEM;
> > +			goto unlock_mutex;
> > +		}
> > +
> > +		cells_attrs[i] = &attrs[i];
> > +		i++;
> > +	}
> > +
> > +	nvmem_cells_group.bin_attrs = cells_attrs;
> > +
> > +	ret = devm_device_add_groups(&nvmem->dev, nvmem_cells_groups);
> > +	if (ret)
> > +		goto unlock_mutex;  
> 
> This is going to create groups after the nvmem device is added, isn't this going to be problem with user space notifications?

Greg said it was not. I hope I understood correctly :-)

And anyway, cells have never been available to userspace, so there is
nothing userspace might expect yet?

Thanks,
Miquèl