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