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1 ========================
2 Linux Switchtec Support
3 ========================
4
5 Microsemi's "Switchtec" line of PCI switch devices is already
6 supported by the kernel with standard PCI switch drivers. However, the
7 Switchtec device advertises a special management endpoint which
8 enables some additional functionality. This includes:
9
10 * Packet and Byte Counters
11 * Firmware Upgrades
12 * Event and Error logs
13 * Querying port link status
14 * Custom user firmware commands
15
16 The switchtec kernel module implements this functionality.
17
18
19 Interface
20 =========
21
22 The primary means of communicating with the Switchtec management firmware is
23 through the Memory-mapped Remote Procedure Call (MRPC) interface.
24 Commands are submitted to the interface with a 4-byte command
25 identifier and up to 1KB of command specific data. The firmware will
26 respond with a 4 bytes return code and up to 1KB of command specific
27 data. The interface only processes a single command at a time.
28
29
30 Userspace Interface
31 ===================
32
33 The MRPC interface will be exposed to userspace through a simple char
34 device: /dev/switchtec#, one for each management endpoint in the system.
35
36 The char device has the following semantics:
37
38 * A write must consist of at least 4 bytes and no more than 1028 bytes.
39 The first four bytes will be interpreted as the command to run and
40 the remainder will be used as the input data. A write will send the
41 command to the firmware to begin processing.
42
43 * Each write must be followed by exactly one read. Any double write will
44 produce an error and any read that doesn't follow a write will
45 produce an error.
46
47 * A read will block until the firmware completes the command and return
48 the four bytes of status plus up to 1024 bytes of output data. (The
49 length will be specified by the size parameter of the read call --
50 reading less than 4 bytes will produce an error.
51
52 * The poll call will also be supported for userspace applications that
53 need to do other things while waiting for the command to complete.
54
55 The following IOCTLs are also supported by the device:
56
57 * SWITCHTEC_IOCTL_FLASH_INFO - Retrieve firmware length and number
58 of partitions in the device.
59
60 * SWITCHTEC_IOCTL_FLASH_PART_INFO - Retrieve address and lengeth for
61 any specified partition in flash.
62
63 * SWITCHTEC_IOCTL_EVENT_SUMMARY - Read a structure of bitmaps
64 indicating all uncleared events.
65
66 * SWITCHTEC_IOCTL_EVENT_CTL - Get the current count, clear and set flags
67 for any event. This ioctl takes in a switchtec_ioctl_event_ctl struct
68 with the event_id, index and flags set (index being the partition or PFF
69 number for non-global events). It returns whether the event has
70 occurred, the number of times and any event specific data. The flags
71 can be used to clear the count or enable and disable actions to
72 happen when the event occurs.
73 By using the SWITCHTEC_IOCTL_EVENT_FLAG_EN_POLL flag,
74 you can set an event to trigger a poll command to return with
75 POLLPRI. In this way, userspace can wait for events to occur.
76
77 * SWITCHTEC_IOCTL_PFF_TO_PORT and SWITCHTEC_IOCTL_PORT_TO_PFF convert
78 between PCI Function Framework number (used by the event system)
79 and Switchtec Logic Port ID and Partition number (which is more
80 user friendly).