From: Samuel Tardieu <sam@inf.enst.fr>
To: Claus Jarnik <jarnik@esk.fhg.de>
Cc: ecos-discuss@sourceware.cygnus.com
Subject: Re: [ECOS] Ethernet driver /MPC860 FADS
Date: Mon, 20 Dec 1999 02:23:00 -0000 [thread overview]
Message-ID: <1999-12-20-11-22-52+trackit+sam@inf.enst.fr> (raw)
In-Reply-To: <385E01EF.727F5845@esk.fhg.de>
| I use the eCos cyg_io_read and cyg_io_write function for
| receive/transmit data.
| (cyg_io_write(cyg_io_handle_t handle, const void *buf, cyg_uint32 *len)
|
| In these functions I copy the data from/to buf with the desired length
| len. This copying (I use memcpy) costs a lot of performance.
Those functions are as close as possible of the read() and write() classical
form. I would suggest that you do not use it for memory mapped devices (such
as the ethernet part of the MPC860) as the data is already available in memory
and you will not be able to prevent the copy. Those functions were designed
originally to read/write from/to a file, with the content loaded on demand,
without needing any extra copy.
So my suggestion is: do not use this if you need to avoid useless copies.
prev parent reply other threads:[~1999-12-20 2:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-20 2:16 Claus Jarnik
1999-12-20 2:23 ` Samuel Tardieu [this message]
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