x86 ATA: Don't touch the size entry for the BIOS disk based device ...

Only the platform sets this entry to setup the correct size or
signals the driver to guess the size of the attached disk.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>

Don't try to guess the size of a disk if its size value is already given ...

Guessing the size of an attached harddisk (access via x86 BIOS) was needed
due to the fact, barebox can't query this information from the BIOS easily.

But with the SD/MMC cards, there will be a second user of the generic disk
handling routines. And with this media it is very easy to know its size.

This patch provides a workaround to keep the guessing feature if the size of
the registered disk is 0. If it is not 0, the given value will be used instead.

Note: This is in preparation to add MCI card support, which can be handled
like a disk drive.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Don't use a sector buffer on stack ...

Using a temp. buffer for a disk sector on the stack, seems not work. Doing so
lets the system run crazy (the stack seems to be destroyd). Don't know the
correct stack handling on ARM, but (IMHO) I also can exclude any writing across
the buffer boundaries.

Using a temp. buffer via malloc() runs also on ARM.

Note: This patch was required to add MCI card support, which can be handled
like a disk drive.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Make the disk driver less noisy ...

In real life this output is only a "nice to have", but most of the time
its useless and confusing. So, make it a debug feature for the interested
developer.

Note: This is in preparation to add MCI card support, which mostly come with
a partition table and can be handled like a disk drive.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

x-functions do not return in case of failure. ...

Remove error handling, because in case of failure the xzalloc() function
does not return.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Add a low level disk drive access driver ...

This is a low level disk drive communication driver. It uses the real mode
BIOS found on most x86 platforms, to read and write sectors. Used by the
generic disk driver.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Add the main disk driver ...

This is the generic disk driver. It does not know how to access the drives.
Other low level drivers are required for this.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Start to add ATA support to barebox ...

Add the basic files, declarations and folders to bring in ATA support.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>