At the moment the nvme_get_features() and nvme_set_features() functions
carry a (somewhat misleading) comment about missing cache maintenance.
As it turns out, nvme_get_features() has no caller at all in the tree,
and nvme_set_features' only user doesn't use a DMA buffer.
Mention that in the comment, and leave some breadcrumbs for the future,
should those functions attract more users.
Signed-off-by: Andre Przywara <andre.przyw...@arm.com>
---
Hi,
just extending the comments as this caused some confusion lately, and to
keep the pointer to the NVMe spec I checked.
Cheers,
Andre
drivers/nvme/nvme.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff --git a/drivers/nvme/nvme.c b/drivers/nvme/nvme.c
index 5d6331ad346..3ff3d5de08e 100644
--- a/drivers/nvme/nvme.c
+++ b/drivers/nvme/nvme.c
@@ -481,6 +481,7 @@ int nvme_get_features(struct nvme_dev *dev, unsigned fid,
unsigned nsid,
dma_addr_t dma_addr, u32 *result)
{
struct nvme_command c;
+ int ret;
memset(&c, 0, sizeof(c));
c.features.opcode = nvme_admin_get_features;
@@ -488,12 +489,20 @@ int nvme_get_features(struct nvme_dev *dev, unsigned fid,
unsigned nsid,
c.features.prp1 = cpu_to_le64(dma_addr);
c.features.fid = cpu_to_le32(fid);
+ ret = nvme_submit_admin_cmd(dev, &c, result);
+
/*
- * TODO: add cache invalidate operation when the size of
- * the DMA buffer is known
+ * TODO: Add some cache invalidation when a DMA buffer is involved
+ * in the request, here and before the command gets submitted. The
+ * buffer size varies by feature, also some features use a different
+ * field in the command packet to hold the buffer address.
+ * Section 5.21.1 (Set Features command) in the NVMe specification
+ * details the buffer requirements for each feature.
+ *
+ * At the moment there is no user of this function.
*/
- return nvme_submit_admin_cmd(dev, &c, result);
+ return ret;
}
int nvme_set_features(struct nvme_dev *dev, unsigned fid, unsigned dword11,
@@ -508,8 +517,14 @@ int nvme_set_features(struct nvme_dev *dev, unsigned fid,
unsigned dword11,
c.features.dword11 = cpu_to_le32(dword11);
/*
- * TODO: add cache flush operation when the size of
- * the DMA buffer is known
+ * TODO: Add a cache clean (aka flush) operation when a DMA buffer is
+ * involved in the request. The buffer size varies by feature, also
+ * some features use a different field in the command packet to hold
+ * the buffer address. Section 5.21.1 (Set Features command) in the
+ * NVMe specification details the buffer requirements for each
+ * feature.
+ * At the moment the only user of this function is not using
+ * any DMA buffer at all.
*/
return nvme_submit_admin_cmd(dev, &c, result);
--
2.17.5
