[PATCH 1/2] doc: develop: Convert README.virtio to reST
Bin Meng
bmeng.cn at gmail.com
Thu Apr 29 11:40:07 CEST 2021
This convers the existing README.virtio to reST, and puts it under
the develop/driver-model/ directory.
Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
---
doc/develop/driver-model/index.rst | 1 +
.../driver-model/virtio.rst} | 90 +++++++++++++------
2 files changed, 63 insertions(+), 28 deletions(-)
rename doc/{README.virtio => develop/driver-model/virtio.rst} (86%)
diff --git a/doc/develop/driver-model/index.rst b/doc/develop/driver-model/index.rst
index fd4575db9b..10a76256b0 100644
--- a/doc/develop/driver-model/index.rst
+++ b/doc/develop/driver-model/index.rst
@@ -27,3 +27,4 @@ subsystems
soc-framework
spi-howto
usb-info
+ virtio
diff --git a/doc/README.virtio b/doc/develop/driver-model/virtio.rst
similarity index 86%
rename from doc/README.virtio
rename to doc/develop/driver-model/virtio.rst
index d3652f2e2f..8ac9c94caf 100644
--- a/doc/README.virtio
+++ b/doc/develop/driver-model/virtio.rst
@@ -1,11 +1,10 @@
-# SPDX-License-Identifier: GPL-2.0+
-#
-# Copyright (C) 2018, Bin Meng <bmeng.cn at gmail.com>
+.. SPDX-License-Identifier: GPL-2.0+
+.. sectionauthor:: Bin Meng <bmeng.cn at gmail.com>
VirtIO Support
==============
-This document describes the information about U-Boot support for VirtIO [1]
+This document describes the information about U-Boot support for VirtIO_
devices, including supported boards, build instructions, driver details etc.
What's VirtIO?
@@ -15,7 +14,7 @@ just the guest's device driver "knows" it is running in a virtual environment,
and cooperates with the hypervisor. This enables guests to get high performance
network and disk operations, and gives most of the performance benefits of
paravirtualization. In the U-Boot case, the guest is U-Boot itself, while the
-virtual environment are normally QEMU [2] targets like ARM, RISC-V and x86.
+virtual environment are normally QEMU_ targets like ARM, RISC-V and x86.
Status
------
@@ -49,6 +48,8 @@ Building U-Boot for pre-configured QEMU targets is no different from others.
For example, we can do the following with the CROSS_COMPILE environment
variable being properly set to a working toolchain for ARM:
+.. code-block:: bash
+
$ make qemu_arm_defconfig
$ make
@@ -56,11 +57,13 @@ You can even create a QEMU ARM target with VirtIO devices showing up on both
MMIO and PCI buses. In this case, you can enable the PCI transport driver
from 'make menuconfig':
-Device Drivers --->
- ...
- VirtIO Drivers --->
- ...
- [*] PCI driver for virtio devices
+.. code-block:: none
+
+ Device Drivers --->
+ ...
+ VirtIO Drivers --->
+ ...
+ [*] PCI driver for virtio devices
Other drivers are at the same location and can be tuned to suit the needs.
@@ -74,6 +77,8 @@ Testing
The following QEMU command line is used to get U-Boot up and running with
VirtIO net and block devices on ARM.
+.. code-block:: bash
+
$ qemu-system-arm -nographic -machine virt -bios u-boot.bin \
-netdev tap,ifname=tap0,id=net0 \
-device virtio-net-device,netdev=net0 \
@@ -82,6 +87,8 @@ VirtIO net and block devices on ARM.
On x86, command is slightly different to create PCI VirtIO devices.
+.. code-block:: bash
+
$ qemu-system-i386 -nographic -bios u-boot.rom \
-netdev tap,ifname=tap0,id=net0 \
-device virtio-net-pci,netdev=net0 \
@@ -93,6 +100,8 @@ parameters. It is also possible to specify both MMIO and PCI VirtIO devices.
For example, the following commnad creates 3 VirtIO devices, with 1 on MMIO
and 2 on PCI bus.
+.. code-block:: bash
+
$ qemu-system-arm -nographic -machine virt -bios u-boot.bin \
-netdev tap,ifname=tap0,id=net0 \
-device virtio-net-pci,netdev=net0 \
@@ -104,6 +113,8 @@ and 2 on PCI bus.
By default QEMU creates VirtIO legacy devices by default. To create non-legacy
(aka modern) devices, pass additional device property/value pairs like below:
+.. code-block:: bash
+
$ qemu-system-i386 -nographic -bios u-boot.rom \
-netdev tap,ifname=tap0,id=net0 \
-device virtio-net-pci,netdev=net0,disable-legacy=true,disable-modern=false \
@@ -112,6 +123,8 @@ By default QEMU creates VirtIO legacy devices by default. To create non-legacy
A 'virtio' command is provided in U-Boot shell.
+.. code-block:: none
+
=> virtio
virtio - virtio block devices sub-system
@@ -127,10 +140,14 @@ A 'virtio' command is provided in U-Boot shell.
To probe all the VirtIO devices, type:
+.. code-block:: none
+
=> virtio scan
Then we can show the connected block device details by:
+.. code-block:: none
+
=> virtio info
Device 0: QEMU VirtIO Block Device
Type: Hard Disk
@@ -138,6 +155,8 @@ Then we can show the connected block device details by:
And list the directories and files on the disk by:
+.. code-block:: none
+
=> ls virtio 0 /
<DIR> 4096 .
<DIR> 4096 ..
@@ -167,6 +186,8 @@ Driver Internals
----------------
There are 3 level of drivers in the VirtIO driver family.
+.. code-block:: none
+
+---------------------------------------+
| virtio device drivers |
| +-------------+ +------------+ |
@@ -199,20 +220,26 @@ The transport drivers provide a set of ops (struct dm_virtio_ops) for the real
virtio device driver to call. These ops APIs's parameter is designed to remind
the caller to pass the correct 'struct udevice' id of the virtio device, eg:
-int virtio_get_status(struct udevice *vdev, u8 *status)
+.. code-block:: C
+
+ int virtio_get_status(struct udevice *vdev, u8 *status)
So the parameter 'vdev' indicates the device should be the real virtio device.
But we also have an API like:
-struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num,
- unsigned int vring_align,
- struct udevice *udev)
+.. code-block:: C
+
+ struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num,
+ unsigned int vring_align,
+ struct udevice *udev)
Here the parameter 'udev' indicates the device should be the transport device.
Similar naming is applied in other functions that are even not APIs, eg:
-static int virtio_uclass_post_probe(struct udevice *udev)
-static int virtio_uclass_child_pre_probe(struct udevice *vdev)
+.. code-block:: C
+
+ static int virtio_uclass_post_probe(struct udevice *udev)
+ static int virtio_uclass_child_pre_probe(struct udevice *vdev)
So it's easy to tell which device these functions are operating on.
@@ -223,20 +250,29 @@ ID 2) are supported. If you want to develop new driver for new devices,
please follow the guideline below.
1. add new device ID in virtio.h
-#define VIRTIO_ID_XXX X
+
+.. code-block:: C
+
+ #define VIRTIO_ID_XXX X
2. update VIRTIO_ID_MAX_NUM to be the largest device ID plus 1
3. add new driver name string in virtio.h
-#define VIRTIO_XXX_DRV_NAME "virtio-xxx"
+
+.. code-block:: C
+
+ #define VIRTIO_XXX_DRV_NAME "virtio-xxx"
4. create a new driver with name set to the name string above
-U_BOOT_DRIVER(virtio_xxx) = {
- .name = VIRTIO_XXX_DRV_NAME,
- ...
- .remove = virtio_reset,
- .flags = DM_FLAG_ACTIVE_DMA,
-}
+
+.. code-block:: C
+
+ U_BOOT_DRIVER(virtio_xxx) = {
+ .name = VIRTIO_XXX_DRV_NAME,
+ ...
+ .remove = virtio_reset,
+ .flags = DM_FLAG_ACTIVE_DMA,
+ }
Note the driver needs to provide the remove method and normally this can be
hooked to virtio_reset(). The driver flags should contain DM_FLAG_ACTIVE_DMA
@@ -247,7 +283,5 @@ for the remove method to be called before jumping to OS.
6. do funny stuff with the driver
-References
-----------
-[1] http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.pdf
-[2] https://www.qemu.org
+.. _VirtIO: http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.pdf
+.. _QEMU: https://www.qemu.org
--
2.25.1
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