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nvmem: core: fix bit offsets of more than one byte

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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: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20250411112251.68002-9-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dmitry Baryshkov 2025-04-11 12:22:46 +01:00 committed by Greg Kroah-Hartman
parent eed6d95454
commit 7a06ef7510
1 changed files with 17 additions and 7 deletions
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24
drivers/nvmem/core.c
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@ -837,7 +837,9 @@ static int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct device_nod
if (addr && len == (2 * sizeof(u32))) { if (addr && len == (2 * sizeof(u32))) {
info.bit_offset = be32_to_cpup(addr++); info.bit_offset = be32_to_cpup(addr++);
info.nbits = 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); dev_err(dev, "nvmem: invalid bits on %pOF\n", child);
of_node_put(child); of_node_put(child);
return -EINVAL; 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) static void nvmem_shift_read_buffer_in_place(struct nvmem_cell_entry *cell, void *buf)
{ {
u8 *p, *b; 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; 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 */ /* First shift */
*b++ >>= bit_offset; *p = *b++ >> bit_offset;
/* setup rest of the bytes if any */ /* setup rest of the bytes if any */
for (i = 1; i < cell->bytes; i++) { for (i = 1; i < cell->bytes; i++) {
/* Get bits from next byte and shift them towards msb */ /* 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; *p = *b++ >> bit_offset;
*b++ >>= bit_offset;
} }
} else if (p != b) {
memmove(p, b, cell->bytes - bytes_offset);
p += cell->bytes - 1;
} else { } else {
/* point to the msb */ /* point to the msb */
p += cell->bytes - 1; p += cell->bytes - 1;