Re: [PATCH v4 iproute2 2/7] rdma: Add dev object

On Tue, Aug 15, 2017 at 04:23:11PM +0000, David Laight wrote:

From: Stephen Hemminger

quoted

Sent: 15 August 2017 17:12
On Tue, 15 Aug 2017 16:00:15 +0300
Leon Romanovsky [off-list ref] wrote:

quoted

+
+static const char *dev_caps_to_str(uint32_t idx)
+{
+	uint64_t cap = 1 << idx;
+
+	switch (cap) {
+	case RDMA_DEV_RESIZE_MAX_WR: return "RESIZE_MAX_WR";
+	case RDMA_DEV_BAD_PKEY_CNTR: return "BAD_PKEY_CNTR";

...

quoted

quoted

+	case RDMA_DEV_RAW_SCATTER_FCS: return "RAW_SCATTER_FCS";
+	case RDMA_DEV_RDMA_NETDEV_OPA_VNIC: return "RDMA_NETDEV_OPA_VNIC";
+	default: return "UNKNOWN";
+	}

Could this be a table in future versions?

Potentially you could define the constants using some pre-processor
'magic' that would create the table for you.
Something like (but not compiled):

#define RDMA_DEV_FLAGS(x) \
	x(RESIZE_MAX_WR, 0) \
	x(BAD_PKEY_CNTR, 1) \
(continue for all the bits)

#define RDMA_DEV_ENUM(name, bit_no) RDMA_DEV_##name = BIT(bit_no),
enum {RDMA_DEV_FLAGS(RDMA_DEV_ENUM)};
#undef RDMA_DEV_ENUM

#define RDMA_DEV_NAMES(name, bit_no) [bit_no] = #name,
static const char rdma_dev_names[] = {RDMA_DEV_FLAGS(RDMA_DEV_NAMES)};

David,

How should I handle "uknown" fields without names?

Thanks

	David

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From: Leon Romanovsky

Sent: 15 August 2017 17:47
On Tue, Aug 15, 2017 at 04:23:11PM +0000, David Laight wrote:

quoted

From: Stephen Hemminger

quoted

Sent: 15 August 2017 17:12
On Tue, 15 Aug 2017 16:00:15 +0300
Leon Romanovsky [off-list ref] wrote:

quoted

+
+static const char *dev_caps_to_str(uint32_t idx)
+{
+	uint64_t cap = 1 << idx;
+
+	switch (cap) {
+	case RDMA_DEV_RESIZE_MAX_WR: return "RESIZE_MAX_WR";
+	case RDMA_DEV_BAD_PKEY_CNTR: return "BAD_PKEY_CNTR";

...

quoted

quoted

+	case RDMA_DEV_RAW_SCATTER_FCS: return "RAW_SCATTER_FCS";
+	case RDMA_DEV_RDMA_NETDEV_OPA_VNIC: return "RDMA_NETDEV_OPA_VNIC";
+	default: return "UNKNOWN";
+	}

Could this be a table in future versions?

Potentially you could define the constants using some pre-processor
'magic' that would create the table for you.
Something like (but not compiled):

#define RDMA_DEV_FLAGS(x) \
	x(RESIZE_MAX_WR, 0) \
	x(BAD_PKEY_CNTR, 1) \
(continue for all the bits)

#define RDMA_DEV_ENUM(name, bit_no) RDMA_DEV_##name = BIT(bit_no),
enum {RDMA_DEV_FLAGS(RDMA_DEV_ENUM)};
#undef RDMA_DEV_ENUM

#define RDMA_DEV_NAMES(name, bit_no) [bit_no] = #name,
static const char rdma_dev_names[] = {RDMA_DEV_FLAGS(RDMA_DEV_NAMES)};

I missed the #undef

quoted

David,

How should I handle "uknown" fields without names?

The function that accesses rdma_dev_names[] checks ARRAY_SIZE()
and for a NULL pointer.

WRT the other comment, the spare pointers consume far less space than
the code for your switch statement.

	David