From: Rafał Miłecki <rafal@xxxxxxxxxx> Broadcom based home router devices use partitions which have to be discovered in a specific way. They are not fixed and there is not any standard partition table. This commit adds and describes a new custom binding for such devices. Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx> --- This commit documents a new binding for describing partitions. Just as a reminder: we agreed to use "compatible" for that purpose to avoid /guessing/. There are too many cases, devices and /formats/ to just blindly try every possible parser. This was e.g. described by Boris in his patchset 2+ years ago: [RFC PATCH 0/7] mtd: partitions: add of_match_table support http://lists.infradead.org/pipermail/linux-mtd/2015-December/064076.html Quote: > (2) we can't just scan for all supported parsers (like the block system does), since > there is a wide diversity of "formats" (no standardization), and it is not > always safe or efficient to attempt to do so, particularly since many of > them allow their data structures to be placed anywhere on the flash, and > so require scanning the entire flash device to find them. I believe this solution was also acked back then by Rob: [RFC PATCH 3/7] doc: dt: mtd: partition: add on-flash format binding http://lists.infradead.org/pipermail/linux-mtd/2015-December/064100.html V2: Move documentation to the new brcm,bcm947xx-cfe-partitions.txt file as suggested by Rob (we don't want to bloat partition.txt). Slightly update commit message. --- .../devicetree/bindings/mtd/partition.txt | 2 +- .../partitions/brcm,bcm947xx-cfe-partitions.txt | 42 ++++++++++++++++++++++ 2 files changed, 43 insertions(+), 1 deletion(-) create mode 100644 Documentation/devicetree/bindings/mtd/partitions/brcm,bcm947xx-cfe-partitions.txt diff --git a/Documentation/devicetree/bindings/mtd/partition.txt b/Documentation/devicetree/bindings/mtd/partition.txt index 36f3b769a626..a8f382642ba9 100644 --- a/Documentation/devicetree/bindings/mtd/partition.txt +++ b/Documentation/devicetree/bindings/mtd/partition.txt @@ -14,7 +14,7 @@ method is used for a given flash device. To describe the method there should be a subnode of the flash device that is named 'partitions'. It must have a 'compatible' property, which is used to identify the method to use. -We currently only document a binding for fixed layouts. +Available bindings are listed in the "partitions" subdirectory. Fixed Partitions diff --git a/Documentation/devicetree/bindings/mtd/partitions/brcm,bcm947xx-cfe-partitions.txt b/Documentation/devicetree/bindings/mtd/partitions/brcm,bcm947xx-cfe-partitions.txt new file mode 100644 index 000000000000..1d61a029395e --- /dev/null +++ b/Documentation/devicetree/bindings/mtd/partitions/brcm,bcm947xx-cfe-partitions.txt @@ -0,0 +1,42 @@ +Broadcom BCM47xx Partitions +=========================== + +Broadcom is one of hardware manufacturers providing SoCs (BCM47xx) used in +home routers. Their BCM947xx boards using CFE bootloader have several partitions +without any on-flash partition table. On some devices their sizes and/or +meanings can also vary so fixed partitioning can't be used. + +Discovering partitions on these devices is possible thanks to having a special +header and/or magic signature at the beginning of each of them. They are also +block aligned which is important for determinig a size. + +Most of partitions use ASCII text based magic for determining a type. More +complex partitions (like TRX with its HDR0 magic) may include extra header +containing some details, including a length. + +A list of supported partitions includes: +1) Bootloader with Broadcom's CFE (Common Firmware Environment) +2) NVRAM with configuration/calibration data +3) Device manufacturer's data with some default values (e.g. SSIDs) +4) TRX firmware container which can hold up to 4 subpartitions +5) Backup TRX firmware used after failed upgrade + +As mentioned earlier, role of some partitions may depend on extra configuration. +For example both: main firmware and backup firmware use the same TRX format with +the same header. To distinguish currently used firmware a CFE's environment +variable "bootpartition" is used. + + +Devices using Broadcom partitions described above should should have flash node +with a subnode named "partitions" using following properties: + +Required properties: +- compatible : (required) must be "brcm,bcm947xx-cfe-partitions" + +Example: + +flash@0 { + partitions { + compatible = "brcm,bcm947xx-cfe-partitions"; + }; +}; -- 2.13.6 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
