Re: Guidelines to plug NE2K driver in ELKS

Hello Marc-F.,

this is what I could make out so far. The functions that support "select" 
are implemented in elks/fs/select.c. KTCP does the following select call: 
„select(sfd > tcpdevfd ? sfd + 1 : tcpdevfd + 1,  &fdset, NULL, NULL, tv);“ 
In there sfd is the file descriptor for slip and tcpdevfd is the file 
descriptor for the tcpdev device.

The tcpdev device has made its tcp_select() function known to the kernel 
using the tcp_fops structure via the register_chrdev() function. The kernel 
calls this function when loading the module. So the kernel can call 
tcp_select() to determine if there is anything to do.

After slip opens the ttySx device, the kernel will query the tty_select() 
function in the arch/i86/drivers/char/ntty driver. I think that again calls 
rs_ioctl() in serial.c. The structure "tty" which is returned by this 
function contains a pointer to the queue of received chars and the select 
function in ntty uses that to determine if data has been received and is 
available for a read call.

One could probably just make a quick and dirty solution and poll the network 
card code for data from the ktcp_run() loop without select. The slip_process 
function just returns if no data has been read.

To follow the Linux structure, however, you would have to write an „ethx“ 
device driver which supports a select call from the kernel.

I am about to finish an "Introduction to ELKS" document this week. The 
document is intended to provide a quick start for new users/developers of 
ELKS. This document contains a chapter how to write a kernel mode driver for 
ELKS although is not typically part of an introduction. If you have not 
written such a driver yet this could be of help for developing an „ethx“ 
device driver.

Georg

-----Ursprüngliche Nachricht----- 
From: Marc-F. LUCCA-DANIAU
Sent: Sunday, February 5, 2017 12:12 PM
To: ELKS
Subject: Guidelines to plug NE2K driver in ELKS

Hello all,

As suggested by Alan and Jody, I delivered a standalone code to drive
the NE2K in /elks/arch/i86/drivers/net as a first step, and I intend to
connect it to the low end of KTCP (in parallel of SLIP) as a second step.

But because KTCP needs a "selectable" device to operate, and because I
am not at ease with the select / poll implementation in ELKS, could I
have some guidelines to integrate the current standalone code ?

Thanks,

MFLD


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