On Fri, Aug 10, 2012 at 11:42 PM, Stefan Hajnoczi <stefa...@gmail.com> wrote: > On Fri, Aug 10, 2012 at 01:54:26PM +1000, Peter A. G. Crosthwaite wrote: >> The sizep arg is populated with the size of the loaded device tree. Since >> this >> is one of those informational "please populate" type arguments it should be >> optional. Guarded writes to *sizep against NULL accordingly. >> >> Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwa...@petalogix.com> >> Acked-by: Alexander Graf <ag...@suse.de> >> --- >> device_tree.c | 8 ++++++-- >> 1 files changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/device_tree.c b/device_tree.c >> index d7a9b6b..641a48a 100644 >> --- a/device_tree.c >> +++ b/device_tree.c >> @@ -71,7 +71,9 @@ void *load_device_tree(const char *filename_path, int >> *sizep) >> int ret; >> void *fdt = NULL; >> >> - *sizep = 0; >> + if (sizep) { >> + *sizep = 0; >> + } >> dt_size = get_image_size(filename_path); >> if (dt_size < 0) { >> printf("Unable to get size of device tree file '%s'\n", >> @@ -104,7 +106,9 @@ void *load_device_tree(const char *filename_path, int >> *sizep) >> filename_path); >> goto fail; >> } >> - *sizep = dt_size; >> + if (sizep) { >> + *sizep = dt_size; >> + } > > What can the caller do with this void* buffer without knowing its size? >
Sanity check the machine: dtb = load_device_tree( ... ); //dont care how big it is foo = fdt_gep_prop( dtb, ... ); if (foo != object_get_prop(foo_device, foo_prop, ... )) { hw_error("your dtb is bad because ... !\n", ... ); } ... boot(); This happens at machine init, which is quite separate from boot. > They cannot hand the buffer to the guest unless they duplicate the > get_image_size() call, which is pointless, or we're assuming a fixed > size, which is unsafe. I'm asking what the legitimate use case for > sizep == NULL is? Sanity check the dtb without passing it to the guest. My CAD tools emit a DTB for the hardware, but it wont always go through a linux bootloader (E.G. I may want to boot random elfs). I still will pass the CAD generated DTB to QEMU for sanity check however so qemu can give me a nice report of what is and isn't modelled. Regards, Peter > > Stefan