[U-Boot] [PATCH 3/5] Add documentation for USB Host Networking

[Wolfgang Denk <wd@denx.de>]

Dear Simon Glass,

In message <1302642840-6958-3-git-send-email-sjg@chromium.org> you wrote:
> This describes what it is for, devices supported, how to enable for your
> board in U-Boot, setting up the server, and notes about MAC addresses.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
...

> +If you have a supported USB Ethernet adapter you can use it in U-Boot
> +to obtain an IP address and load a kernel from a network server.

I have a few questions.

Is this the only possible use? What about netconsole? What about
getting the time using SNTP? What about loading other files than a
kernel?

> +USB Host Networking is different from making your board act as a USB
> +client. In that case your board is pretending to be an Ethernet adapter
> +and will appear as a network interface to an attached computer. The
> +connection is via a USB cable with the computer acting as the host.

...the computer is the host.

> +With USB Host Networking, your board is the USB host. It controls the

...the board is the host.

I am confused.

> +Ethernet adapter to which it is directly connected and the connection to
> +the outside world is your adapter's Ethernet cable. Your board becomes a
> +first class network device, able to connect and perform network
> +operations independently of your computer.

What is the definition of a "first class network device", what's a
"second class network device", and what's the difference?

> +usb start
> +setenv bootfile /tftpboot/uImage
> +setenv autoload y
> +bootp
> +
> +
> +(The autoload option makes bootp automatically load the boot file.)

Is it necessary to explain unrelated details here?

> +You will also want to enable the network commands:
> +
> +#define CONFIG_CMD_NET
> +#define CONFIG_NET_MULTI
> +#define CONFIG_CMD_PING
> +#define CONFIG_CMD_DHCP

Why these? What about others like NFS or SNTP or NETCONSOLE ?

> +gateway IP, host name and boot path from the bootp/dhcp server:
> +
> +#define CONFIG_BOOTP_SUBNETMASK
> +#define CONFIG_BOOTP_GATEWAY
> +#define CONFIG_BOOTP_HOSTNAME
> +#define CONFIG_BOOTP_BOOTPATH

WHich of this is actually related to USB Host Networking (versus
genral network configuration).

> +You should also set the default IP address of your board and the server
> +as well as the default file to load when a 'bootp' command is issued.
> +
> +#define CONFIG_IPADDR           10.0.0.2
> +#define CONFIG_SERVERIP         10.0.0.1

NAK!!!  This is a reliable way to get a plain NAK when submitting your
code to mainline.

> +Then 'bootp' should use it to obtain an IP address from DHCP, perhaps
> +something like this:

I don't understand why you insist on using bootp here.  I guess dhcp
would work as well, as would a plain tftp ?

> +Server Setup

Unrelated, please delete.

Best regards,

Wolfgang Denk

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DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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