Re: [PATCH 1/2] Initial support for Allwinner's Security ID fuses

[Oliver Schinagl]

On 06/02/13 17:09, Russell King - ARM Linux wrote:
> On Sun, Jun 02, 2013 at 04:58:49PM +0200, Oliver Schinagl wrote:
> > +#include <asm/io.h>
>
> We have an include file called linux/io.h.  Please use linux/*.h files which
> include asm/*.h files in preference to directly using asm/*.h.
>
> In fact, no driver should include an asm/*.h header.
And I didn't have that there, but it kept refusing to find ioread32be. 
Of course, now I change it back to linux/io.h (which I had, I swear) and 
all works swell.

Concider it changed.
> > +#include <linux/compiler.h>
> > +#include <linux/device.h>
> > +#include <linux/err.h>
> > +#include <linux/errno.h>
> > +#include <linux/export.h>
> > +#include <linux/fs.h>
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/kobject.h>
> > +#include <linux/module.h>
> > +#include <linux/of_address.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/random.h>
> > +#include <linux/stat.h>
> > +#include <linux/sysfs.h>
> > +#include <linux/types.h>
> > +
> > +#define DRV_NAME "sunxi-sid"
> > +#define DRV_VERSION "1.0"
> > +
> > +/* There are 4 32-bit keys */
> > +#define SID_KEYS 4
> > +/* and 4 byte sized keys per 32-bit key */
> > +#define SID_SIZE (SID_KEYS * 4)
> > +
> > +static void __iomem *p_sid_reg_base;
> > +
> > +/* We read the entire key, but only return the requested byte. This is of
> > + * course slower then it could be and uses 4 times more reads as needed but
> > + * keeps code a simpler.
> > + */
> > +u8 sunxi_sid_read_byte(const int offset)
> > +{
> > +	u32 sid_key;
> > +	u8 ret;
> > +
> > +	ret = 0;
> > +
> > +	if (likely((SID_SIZE))) {
> > +		sid_key = ioread32be(p_sid_reg_base + round_down(offset, 4));
> > +		sid_key >>= (offset % 4) * 8;
> > +		ret = sid_key & 0xff;
> > +	}
>
> What happens if you unbind the device in sysfs and then try and use
> this function?
>
> > +static int sunxi_sid_remove(struct platform_device *pdev)
> > +{
> > +	device_remove_bin_file(&pdev->dev, &sid_bin_attr);
> > +	dev_info(&pdev->dev, "Sunxi SID driver unloaded successfully.\n");
>
> Maybe you want to set p_sid_reg_base to NULL here?
>
> > +
> > +	return 0;
> > +}
> > +
> > +static int __init sunxi_sid_probe(struct platform_device *pdev)
> > +{
> > +	int entropy[SID_SIZE], i, ret;
> > +	struct device *dev;
> > +	struct resource *res;
> > +	void __iomem *sid_reg_base;
> > +
> > +	dev = &pdev->dev;
> > +	if (unlikely(!pdev->dev.of_node)) {
> > +		dev_err(dev, "No devicetree data available\n");
> > +		ret = -EFAULT;
> > +		goto exit;
> > +	}
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	sid_reg_base = devm_ioremap_resource(&pdev->dev, res);
> > +	if (IS_ERR(sid_reg_base)) {
> > +		dev_err(dev, "Unable to obtain resource\n");
> > +		ret = PTR_ERR(sid_reg_base);
> > +		goto exit;
> > +	}
> > +	platform_set_drvdata(pdev, sid_reg_base);
> > +	p_sid_reg_base = sid_reg_base;
>
> So what happens if you have two of these devices?  Maybe you want to check
> whether p_sid_reg_base is already set?
>
> > +
> > +	ret = device_create_bin_file(dev, &sid_bin_attr);
> > +	if (unlikely(ret)) {
> > +		dev_err(dev, "Unable to create sysfs bin entry\n");
> > +		goto exit;
> > +	}
> > +
> > +	for (i = 0; i < SID_SIZE; i++)
> > +		entropy[i] = sunxi_sid_read_byte(i);
> > +	add_device_randomness(entropy, SID_SIZE);
> > +
> > +	dev_info(dev, "Sunxi SID driver loaded successfully.\n");
>
> Do we really need to report that the driver "loaded successfully" ?
> Do we need lots of lines in the kernel log telling us simply that
> random driver X was built into the kernel or the module was loaded?

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