On 2/1/21 6:02 PM, Amy Parker wrote:
On Mon, Feb 1, 2021 at 3:32 PM Alex Elder <el...@linaro.org> wrote:
When extracting the destination endpoint ID from the status in
ipa_endpoint_status_skip(), u32_get_bits() is used. This happens to
work, but it's wrong: the structure field is only 8 bits wide
instead of 32.
Fix this by using u8_get_bits() to get the destination endpoint ID.
Isn't
(I saw your second message.)
Signed-off-by: Alex Elder <el...@linaro.org>
---
drivers/net/ipa/ipa_endpoint.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index 448d89da1e456..612afece303f3 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -1164,8 +1164,8 @@ static bool ipa_endpoint_status_skip(struct ipa_endpoint
*endpoint,
return true;
A few lines above this, endpoint_id is initialized as u32. If we're
going for "correctness", endpoint_id should be a u8. But of course,
this would contrast with ipa_endpoint having it as a u32.
You are correct, endpoint_id is *defined* as type u32.
But the issue here is that the field status->endp_dst_idx
has type u8. u32_get_bits() assumes the field it is
passed has type u32; while u8_get_bits() takes a u8.
The return value of u8_get_bits() is u8, as you might
suspect. The C standard guarantees that the u8 value
will be promoted to the u32 target type here.
if (!status->pkt_len)
return true;
- endpoint_id = u32_get_bits(status->endp_dst_idx,
- IPA_STATUS_DST_IDX_FMASK);
+ endpoint_id = u8_get_bits(status->endp_dst_idx,
+ IPA_STATUS_DST_IDX_FMASK);
if (endpoint_id != endpoint->endpoint_id)
return true;
--
2.27.0
As far as I see it, using u32_get_bits instead of u8_get_bits simply
eliminates confusion about the type of endpoint_id. Perhaps instead of
this patch, send a patch with a comment that while u32_get_bits is
used, the field is only 8 bits?
No. We really want to extract a sub-field from the u8
value passed to u8_get_bits() (not u32_get_bits()).
Does that make sense?
-Alex
Best regards,
Amy Parker
(she/her/hers)
