cfe196fbed
The nvmem interface helps provider of nvmem data to expose themselves to consumer. NVMEM is generally present on some embedded board in a form of eeprom or fuses. The nvmem api are helpers for consumer to read/write the cell data from a provider. Differential Revision: https://reviews.freebsd.org/D16419
158 lines
5.1 KiB
Groff
158 lines
5.1 KiB
Groff
.\" Copyright (c) 2018 Emmanuel Vadot <manu@freebsd.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 24, 2018
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.Dt nvmem 9
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.Os
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.Sh NAME
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.Nm nvmem
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.Nm nvmem_get_cell_len ,
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.Nm nvmem_read_cell_by_name ,
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.Nm nvmem_read_cell_by_idx ,
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.Nm nvmem_write_cell_by_name ,
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.Nm nvmem_write_cell_by_idx ,
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.Sh SYNOPSIS
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.Cd "options EXT_RESOURCES"
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.Cd "options FDT"
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.Cd "device nvmem"
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.In sys/extres/nvmem/nvmem.h
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.Ft int
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.Fn nvmem_get_cell_len "phandle_t node" "const char *name"
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.Ft int
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.Fn nvmem_read_cell_by_name "phandle_t node" "const char *name" "void *cell" "size_t buflen"
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.Ft int
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.Fn nvmem_read_cell_by_idx "phandle_t node" "int idx" "void *cell" "size_t buflen"
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.Ft int
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.Fn nvmem_write_cell_by_name "phandle_t node" "const char *name" "void *cell" "size_t buflen"
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.Ft int
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.Fn nvmem_write_cell_by_idx "phandle_t node" "int idx" "void *cell" "size_t buflen"
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.Sh DESCRIPTION
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On some embedded boards, the manufacturer stored some data on a NVMEM
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(Non-Volatile Memory), this is generally stored in some eeprom or fuses.
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.Pp
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The
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.Nm
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API consist of helpers functions for consumer and device methods for
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providers.
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.Sh FUNCTIONS
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.Bl -tag -width indent
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.It Fn nvmem_get_cell_len "phandle_t node" "const char *name"
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Get the size of the cell base on the reg property on the node.
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Return the size or ENOENT if the cell name wasn't found
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.It Fn nvmem_read_cell_by_name "phandle_t node" "const char *name" "void *cell" "size_t buflen"
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Get the cell content based on the name.
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Return 0 on sucess or ENOENT if the cell doesn't exists, ENXIO if no provider device was found,
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EINVAL if the size isn't correct.
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.It Fn nvmem_read_cell_by_idx "phandle_t node" "int idx" "void *cell" "size_t buflen"
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Get the cell content based on the id.
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Return 0 on sucess or ENOENT if the cell doesn't exists, ENXIO if no provider device was found,
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EINVAL if the size isn't correct.
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.It Fn nvmem_write_cell_by_name "phandle_t node" "const char *name" "void *cell" "size_t buflen"
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Write the cell content based on the name.
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Return 0 on sucess or ENOENT if the cell doesn't exists, ENXIO if no provider device was found,
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EINVAL if the size isn't correct.
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.It Fn nvmem_write_cell_by_idx "phandle_t node" "int idx" "void *cell" "size_t buflen"
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Write the cell content based on the id.
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Return 0 on sucess or ENOENT if the cell doesn't exists, ENXIO if no provider device was found,
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EINVAL if the size isn't correct.
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.El
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.Sh DEVICE METHODS
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.Bl -tag -width indent
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.It Fn nvmem_read "device_t dev" "uint32_t offset" "uint32_t size" "uint8_t *buffer"
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Provider device method to read a cell content.
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.It Fn nvmem_write "device_t dev" "uint32_t offset" "uint32_t size" "uint8_t *buffer"
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Provider device method to write a cell content.
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.El
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.Sh EXAMPLES
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Consider this DTS
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.Bd -literal
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/* Provider */
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eeprom: eeprom@20000 {
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board_id: id@0 {
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reg = <0x0 0x4>;
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};
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};
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/* Consumer */
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device@30000 {
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...
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nvmem-cells = <&board_id>
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nvmem-cell-names = "boardid";
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};
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.Ed
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.Pp
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The device driver for eeprom@20000 needs to expose itself as a provider
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.Bd -literal
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#include "nvmem_if.h"
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int
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foo_nvmem_read(device_t dev, uint32_t offset, uint32_t size, uint8_t *buffer)
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{
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/* Read the data */
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}
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int
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foo_attach(device_t dev)
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{
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phandle_t node;
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node = ofw_bus_get_node(dev);
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...
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/* Registering the device so the consumers can find us */
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OF_device_register_xref(OF_xref_from_node(node), dev);
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...
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}
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static device_method_t foo_methods[] = {
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...
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/* nvmem interface */
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DEVMETHOD(nvmem_read, foo_nvmem_read),
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/* Terminate method list */
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DEVMETHOD_END
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};
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.Ed
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.Pp
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The consumer device driver for device@30000 can now read the nvmem data
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.Bd -literal
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int
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bar_attach(device_t dev)
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{
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phandle_t node;
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uint32_t boardid;
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...
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node = ofw_bus_get_node(dev);
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nvmem_read_cell_by_name(node, "boardid", (void *)&boardid, sizeof(boardid));
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...
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}
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.Ed
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.Sh HISTORY
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The nvmem related function first appear in
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.Fx 12.0 .
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The nvmem interface and manual page was written by
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.An Emmanuel Vadot Aq Mt manu@FreeBSD.org .
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