[PATCH v2] applesmc: add sysfs file to report OSK

["Gabriel L. Somlo" <somlo@cmu.edu>]

The AppleSMC contains two char[32] keys, OSK0 and OSK1, which are not
reported in the key count and index by default. These keys are used by
the OS X boot sequence, and normally don't matter when running Linux.

This patch creates a sysfs entry which reports the value of these keys
as an ASCII string, to help emulators (such as QEMU) load OS X when
running on genuine Apple hardware.

Signed-off-by: Gabriel L. Somlo <somlo@cmu.edu>
---

Henrik,

On Mon, Dec 10, 2012 at 09:19:51PM +0100, Alexander Graf wrote:
>
> On Mon, Dec 10, 2012 at 08:54:14PM +0100, Henrik Rydberg wrote:
> >
> > The OSK string seems constant accross machines, which renders the
> > patch rather pointless, no? And even if the OSK differs between a
> > couple of machines, the emulator could easily handle it gracefully.
>
> The point is that the return value of the OSK is a copyrighted string,
> we can not include in any other layer. The only way to make this
> legally savvy is to   read the key from the host.

I believe this second version addresses your stylistic objections.

As Alex pointed out, hardcoding the OSK in any open-source project
might lead to legal/copyright related issues, whereas simply reporting
whatever the the hardware happens to contain should keep everyone safe.

As for struct applesmc_node_group info_group[]:

> > Unfortunately this is not a good place to put random things going
> > forward.

I figured "info_group" for the "least bad" place to put the OSK, given
that it's more or less "information from/about the SMC". If you could be
persuaded by the above arguments to accept the patch, and have a better
place in mind, I'd be happy to move it there...

Thanks again,
 Gabriel

 drivers/hwmon/applesmc.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index b41baff..b37b271 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -1013,6 +1013,24 @@ static ssize_t applesmc_key_at_index_store(struct device *dev,
 	return count;
 }
 
+static ssize_t applesmc_osk_show(struct device *dev,
+				struct device_attribute *attr, char *sysfsbuf)
+{
+	int ret;
+	char buf[65];
+
+	mutex_lock(&smcreg.mutex);
+	ret = read_smc(APPLESMC_READ_CMD, "OSK0", buf, 32);
+	if (!ret)
+		ret = read_smc(APPLESMC_READ_CMD, "OSK1", buf + 32, 32);
+	mutex_unlock(&smcreg.mutex);
+	if (ret)
+		return ret;
+
+	buf[64] = '\0';
+	return snprintf(sysfsbuf, PAGE_SIZE, "%s\n", buf);
+}
+
 static struct led_classdev applesmc_backlight = {
 	.name			= "smc::kbd_backlight",
 	.default_trigger	= "nand-disk",
@@ -1027,6 +1045,7 @@ static struct applesmc_node_group info_group[] = {
 	{ "key_at_index_type", applesmc_key_at_index_type_show },
 	{ "key_at_index_data_length", applesmc_key_at_index_data_length_show },
 	{ "key_at_index_data", applesmc_key_at_index_read_show },
+	{ "osk", applesmc_osk_show },
 	{ }
 };
 
-- 
1.7.7.6