On Tue, Sep 23, 2014 at 04:46:06PM +0200, Antonios Motakis wrote:
> As already demonstrated with PCI [1] and the platform bus [2], a
> driver_override property in sysfs can be used to bypass the id matching
> of a device to a AMBA driver. This can be used by VFIO to bind to any AMBA
> device requested by the user.
>
> [1]
> http://lists-archives.com/linux-kernel/28030441-pci-introduce-new-device-binding-path-using-pci_dev-driver_override.html
> [2] https://www.redhat.com/archives/libvir-list/2014-April/msg00382.html
>
> Signed-off-by: Antonios Motakis <a.mota...@virtualopensystems.com>
I have to ask why this is even needed in the first place. To take the
example in [2], what's wrong with:
echo fff51000.ethernet >
/sys/bus/platform/devices/fff51000.ethernet/driver/unbind
echo fff51000.ethernet > /sys/bus/platform/drivers/vfio-platform/bind
and similar for AMBA.
All we would need to do is to introduce a way of having a driver accept
explicit bind requests.
In any case:
> +static ssize_t driver_override_store(struct device *_dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct amba_device *dev = to_amba_device(_dev);
> + char *driver_override, *old = dev->driver_override, *cp;
> +
> + if (count > PATH_MAX)
> + return -EINVAL;
> +
> + driver_override = kstrndup(buf, count, GFP_KERNEL);
> + if (!driver_override)
> + return -ENOMEM;
> +
> + cp = strchr(driver_override, '\n');
> + if (cp)
> + *cp = '\0';
I hope that is not replicated everywhere. This allows up to a page to be
allocated, even when the first byte may be a newline. This is wasteful.
How about:
if (count > PATH_MAX)
return -EINVAL;
cp = strnchr(buf, count, '\n');
if (cp)
count = cp - buf - 1;
if (count) {
driver_override = kstrndup(buf, count, GFP_KERNEL);
if (!driver_override)
return -ENOMEM;
} else {
driver_override = NULL;
}
kfree(dev->driver_override);
dev->driver_override = driver_override;
Also:
> +static ssize_t driver_override_show(struct device *_dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct amba_device *dev = to_amba_device(_dev);
> +
> + return sprintf(buf, "%s\n", dev->driver_override);
> +}
Do we really want to do a NULL pointer dereference here?
--
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.
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