Commit 7a06ef75 authored by Dmitry Baryshkov's avatar Dmitry Baryshkov Committed by Greg Kroah-Hartman
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nvmem: core: fix bit offsets of more than one byte 



If the NVMEM specifies a stride to access data, reading particular cell
might require bit offset that is bigger than one byte. Rework NVMEM core
code to support bit offsets of more than 8 bits.

Signed-off-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: default avatarSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20250411112251.68002-9-srinivas.kandagatla@linaro.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent eed6d954

drivers/nvmem/core.c

+17 −7
Original line number Diff line number Diff line
@@ -837,7 +837,9 @@ static int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct device_nod 
		if (addr && len == (2 * sizeof(u32))) {

			info.bit_offset = be32_to_cpup(addr++);

			info.nbits = be32_to_cpup(addr);

			if (info.bit_offset >= BITS_PER_BYTE || info.nbits < 1) {

			if (info.bit_offset >= BITS_PER_BYTE * info.bytes ||

			    info.nbits < 1 ||

			    info.bit_offset + info.nbits > BITS_PER_BYTE * info.bytes) {

				dev_err(dev, "nvmem: invalid bits on %pOF\n", child);

				of_node_put(child);

				return -EINVAL;
@@ -1630,21 +1632,29 @@ EXPORT_SYMBOL_GPL(nvmem_cell_put); 
static void nvmem_shift_read_buffer_in_place(struct nvmem_cell_entry *cell, void *buf)

{

	u8 *p, *b;

	int i, extra, bit_offset = cell->bit_offset;

	int i, extra, bytes_offset;

	int bit_offset = cell->bit_offset;



	p = b = buf;

	if (bit_offset) {



	bytes_offset = bit_offset / BITS_PER_BYTE;

	b += bytes_offset;

	bit_offset %= BITS_PER_BYTE;



	if (bit_offset % BITS_PER_BYTE) {

		/* First shift */

		*b++ >>= bit_offset;

		*p = *b++ >> bit_offset;



		/* setup rest of the bytes if any */

		for (i = 1; i < cell->bytes; i++) {

			/* Get bits from next byte and shift them towards msb */

			*p |= *b << (BITS_PER_BYTE - bit_offset);

			*p++ |= *b << (BITS_PER_BYTE - bit_offset);



			p = b;

			*b++ >>= bit_offset;

			*p = *b++ >> bit_offset;

		}

	} else if (p != b) {

		memmove(p, b, cell->bytes - bytes_offset);

		p += cell->bytes - 1;

	} else {

		/* point to the msb */

		p += cell->bytes - 1;