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nvme: improve comment for nvme_pcie_ctrlr_get_max_xfer_size

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NVME_MAX_PRP_LIST_ENTRIES has changed over time, so let's
just remove the reference to the exact value here.  Also
explain a bit more why the max size isn't
(NUM_ENTRIES + 1) * page_size.

While here, do a small whitespace cleanup as well.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: Ib75813788abdd3dbb43192f9fdc27f99b33aeadf
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/7328
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
This commit is contained in:
Jim Harris 2021-04-12 14:45:48 +00:00
parent 17fdcd7116
commit c2e0da84c6
1 changed files with 8 additions and 4 deletions
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12
lib/nvme/nvme_pcie.c
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@ -271,15 +271,19 @@ nvme_pcie_ctrlr_get_cmbsz(struct nvme_pcie_ctrlr *pctrlr, union spdk_nvme_cmbsz_
&cmbsz->raw);
}
static uint32_t
static uint32_t
nvme_pcie_ctrlr_get_max_xfer_size(struct spdk_nvme_ctrlr *ctrlr)
{
/*
* For commands requiring more than 2 PRP entries, one PRP will be
* embedded in the command (prp1), and the rest of the PRP entries
* will be in a list pointed to by the command (prp2). This means
* that real max number of PRP entries we support is 506+1, which
* results in a max xfer size of 506*ctrlr->page_size.
* will be in a list pointed to by the command (prp2). The number
* of PRP entries in the list is defined by
* NVME_MAX_PRP_LIST_ENTRIES.
*
* Note that the max xfer size is not (MAX_ENTRIES + 1) * page_size
* because the first PRP entry may not be aligned on a 4KiB
* boundary.
*/
return NVME_MAX_PRP_LIST_ENTRIES * ctrlr->page_size;
}