[PATCH net-next v2 05/10] net: dsa: debugfs: add port regs

[Vivien Didelot]

Add a debug filesystem "regs" entry to query a port's hardware registers
through the .get_regs_len and .get_regs_len switch operations.

This is very convenient because it allows one to dump the registers of
DSA links, which are not exposed to userspace.

Here are the registers of a zii-rev-b CPU and DSA ports:

    # pr -mt switch0/port{5,6}/regs
     0: 4e07                         0: 4d04
     1: 403e                         1: 003d
     2: 0000                         2: 0000
     3: 3521                         3: 3521
     4: 0533                         4: 373f
     5: 8000                         5: 0000
     6: 005f                         6: 003f
     7: 002a                         7: 002a
     8: 2080                         8: 2080
     9: 0001                         9: 0001
    10: 0000                        10: 0000
    11: 0020                        11: 0000
    12: 0000                        12: 0000
    13: 0000                        13: 0000
    14: 0000                        14: 0000
    15: 9100                        15: dada
    16: 0000                        16: 0000
    17: 0000                        17: 0000
    18: 0000                        18: 0000
    19: 0000                        19: 00d8
    20: 0000                        20: 0000
    21: 0000                        21: 0000
    22: 0022                        22: 0000
    23: 0000                        23: 0000
    24: 3210                        24: 3210
    25: 7654                        25: 7654
    26: 0000                        26: 0000
    27: 8000                        27: 8000
    28: 0000                        28: 0000
    29: 0000                        29: 0000
    30: 0000                        30: 0000
    31: 0000                        31: 0000

Signed-off-by: Vivien Didelot <vivien.dide...@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.faine...@gmail.com>
Reviewed-by: Andrew Lunn <and...@lunn.ch>
---
 net/dsa/debugfs.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/net/dsa/debugfs.c b/net/dsa/debugfs.c
index 997bbc8eb502..7b299c9d9892 100644
--- a/net/dsa/debugfs.c
+++ b/net/dsa/debugfs.c
@@ -109,6 +109,40 @@ static int dsa_debugfs_create_file(struct dsa_switch *ds, 
struct dentry *dir,
        return 0;
 }
 
+static void dsa_debugfs_regs_read_count(struct dsa_switch *ds, int id,
+                                       struct seq_file *seq, int count)
+{
+       u16 data[count * ETH_GSTRING_LEN];
+       struct ethtool_regs regs;
+       int i;
+
+       ds->ops->get_regs(ds, id, &regs, data);
+
+       for (i = 0; i < count / 2; i++)
+               seq_printf(seq, "%2d: %04x\n", i, data[i]);
+}
+
+static int dsa_debugfs_regs_read(struct dsa_switch *ds, int id,
+                                struct seq_file *seq)
+{
+       int count;
+
+       if (!ds->ops->get_regs_len || !ds->ops->get_regs)
+               return -EOPNOTSUPP;
+
+       count = ds->ops->get_regs_len(ds, id);
+       if (count < 0)
+               return count;
+
+       dsa_debugfs_regs_read_count(ds, id, seq, count);
+
+       return 0;
+}
+
+static const struct dsa_debugfs_ops dsa_debugfs_regs_ops = {
+       .read = dsa_debugfs_regs_read,
+};
+
 static void dsa_debugfs_stats_read_count(struct dsa_switch *ds, int id,
                                         struct seq_file *seq, int count)
 {
@@ -188,6 +222,11 @@ static int dsa_debugfs_create_port(struct dsa_switch *ds, 
int port)
        if (IS_ERR_OR_NULL(dir))
                return -EFAULT;
 
+       err = dsa_debugfs_create_file(ds, dir, "regs", port,
+                                     &dsa_debugfs_regs_ops);
+       if (err)
+               return err;
+
        err = dsa_debugfs_create_file(ds, dir, "stats", port,
                                      &dsa_debugfs_stats_ops);
        if (err)
-- 
2.14.1