On 12/13/21 9:06 AM, Chaitanya Kulkarni wrote:

On 12/7/21 5:55 AM, Hannes Reinecke wrote:

quoted

Currently applications have a hard time figuring out which
nvme-over-fabrics arguments are supported for any given kernel;
the ioctl will return an error code on failure, and the application
has to guess whether this was due to an invalid argument or due
to a connection or controller error.
With this patch applications can read a list of supported
arguments by simply reading from /dev/nvme-fabrics, allowing
them to validate the connection string.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
   drivers/nvme/host/fabrics.c | 22 +++++++++++++++++++++-
   1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 282d54117e0a..7ae041e2b3fb 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c

@@ -1069,6 +1069,26 @@ static ssize_t nvmf_dev_write(struct file *file, const char __user *ubuf,
   	return ret ? ret : count;
   }
   
+static void __nvmf_concat_opt_tokens(struct seq_file *seq_file)
+{
+	const struct match_token *tok;
+	int idx;
+
+	/*
+	 * Add dummy entries for instance and cntlid to
+	 * signal an invalid/non-existing controller
+	 */
+	seq_puts(seq_file, "instance=-1,cntlid=-1");
+	for (idx = 0; idx < ARRAY_SIZE(opt_tokens); idx++) {
+		tok = &opt_tokens[idx];
+		if (tok->token == NVMF_OPT_ERR)
+			continue;
+		seq_puts(seq_file, ",");

Can we use "\n" instead of "," ?
with that change it looks :-

instance=-1,cntlid=-1
transport=%s
traddr=%s
trsvcid=%s
nqn=%s
queue_size=%d
nr_io_queues=%d
reconnect_delay=%d
ctrl_loss_tmo=%d
keep_alive_tmo=%d
hostnqn=%s
host_traddr=%s
host_iface=%s
hostid=%s
duplicate_connect
disable_sqflow
hdr_digest
data_digest
nr_write_queues=%d
nr_poll_queues=%d
tos=%d
fast_io_fail_tmo=%d
discovery

The ',' format is being used for a successful connect, so I'd rather 
stay with that to make parsing easier.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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