Hi Bin,
On Sun, 7 Feb 2021 at 22:17, Bin Meng bmeng.cn@gmail.com wrote:
Hi Simon,
On Mon, Feb 8, 2021 at 12:21 PM Simon Glass sjg@chromium.org wrote:
Hi Bin,
On Sun, 7 Feb 2021 at 08:11, Bin Meng bmeng.cn@gmail.com wrote:
At present fdt_read_prop() can only handle 1 or 2 cells. It is called by fdt_read_range() which may be used to read PCI address from <ranges> for a PCI bus node where the number of PCI address cell is 3.
This adds the special handling of such case.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
common/fdt_support.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
I think this is missing why it is needed. Also needs an update to function to the comment in the header file.
I will try to add more details in v2.
The reason why this is needed is because in fdt_read_range() may be used to read PCI address from <ranges>. The <ranges> property is an array of { <child address> <parent address> <size in child address space> }.
When trying to read <child address> from a PCI bus node using fdt_read_prop(), as the codes below:
/* Read <child address> */ if (child_addr) { r = fdt_read_prop(ranges, ranges_len, cell, child_addr, acells); if (r) return r; }it will fail, because the PCI child address is made up of 3 cells but fdt_read_prop() cannot handle it. We advance the cell offset by 1 so that the <child address> can be correctly read.
OK, that could go in the commit message and a function comment somewhere about the case.
There is similar code in decode_regions(), so we have two places that read ranges.
Regards, Simon