image_renderer: Use read_file_2 ...

This returns a proper error code and allows us to print a proper
error message which might not always be -ENOMEM.

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

move file helper functions to separate file ...

We have our file helper functions in several places. Move them
all to lib/libfile.c.
With this we no longer have file helpers in fs/fs.c which contains
the core fs functions and no functions in lib/libbb.c which are
not from busybox.

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

splash: Print error message when no renderer is found ...

the splash command silently fails when no renderer is found for
an image type. Print an error message in this case.

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

filetype: Pass bufsize ...

Pass the buffer size to the file detection code. This makes sure we do not
read past the buffer. This is especially useful for ext filesystem detection
as the magic is at byte offset 1080. Also introduce a FILE_TYPE_SAFE_BUFSIZE
define which is set to the minimum bufsize the detection code needs to detect
all known filetypes.

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

gui: introduce screen and surface to factorize and simplify code ...

Instead of passing hundreds of parameter, just pass the right structure.

struct screen represent the screen with a without double buffering.
struct surface represent the part of the screen we want to render.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

gui: move gui file to include/gui and lib/gui ...

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>