linux-kernel - Re: [PATCH v3 1/2] firmware: google: Expose CBMEM over sysfs

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Date:   Thu, 19 Dec 2019 18:17:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     patrick.rudolph@...ements.com
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Allison Randal <allison@...utok.net>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Samuel Holland <samuel@...lland.org>,
        Julius Werner <jwerner@...omium.org>
Subject: Re: [PATCH v3 1/2] firmware: google: Expose CBMEM over sysfs

On Thu, Nov 28, 2019 at 01:50:50PM +0100, patrick.rudolph@...ements.com wrote:
> +static int cbmem_probe(struct coreboot_device *cdev)
> +{
> +	struct device *dev = &cdev->dev;
> +	struct cb_priv *priv;
> +	int err;
> +
> +	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	memcpy(&priv->entry, &cdev->cbmem_entry, sizeof(priv->entry));
> +
> +	priv->remap = memremap(priv->entry.address,
> +			       priv->entry.entry_size, MEMREMAP_WB);
> +	if (!priv->remap) {
> +		err = -ENOMEM;
> +		goto failure;
> +	}
> +
> +	err = sysfs_create_group(&dev->kobj, &cb_mem_attr_group);

You just raced with userspace and lost :(

Set the driver's default attribute group up to point at
cb_mem_attr_group and the driver core will handle creating and removing
the group automatically for you correctly.

thanks,

greg k-h