diff mbox series

[v4,1/5] nvmem: core: fix bit offsets of more than one byte

Message ID 20250109-sar2130p-nvmem-v4-1-633739fe5f11@linaro.org
State New
Headers show
Series [v4,1/5] nvmem: core: fix bit offsets of more than one byte | expand

Commit Message

Dmitry Baryshkov Jan. 9, 2025, 4:35 a.m. UTC 
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>
---
 drivers/nvmem/core.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

Comments

Dmitry Baryshkov Feb. 4, 2025, 11:40 p.m. UTC | #1 
On Thu, Jan 09, 2025 at 06:35:45AM +0200, Dmitry Baryshkov wrote:
> 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>
> ---
>  drivers/nvmem/core.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)

Srinivas, it has been almost a month ago, we are past the merge window.
Could you please review the patchset? I'd like to understand if we need
to spend more time on it or if it is fine.
diff mbox series

Patch

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index d6494dfc20a7324bde6415776dcabbb0bfdd334b..7fa85b0804db360035d7471002dbf79658d5830b 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -834,7 +834,9 @@  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;
@@ -1627,21 +1629,29 @@  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;