[from old commit log]

In article <20050323202308.2BDE62DA27@cvs.netbsd.org>
yamt@netbsd.org wrote:

> Module Name:	src
> Committed By:	yamt
> Date:		Wed Mar 23 20:23:08 UTC 2005
> 
> Modified Files:
> 	src/sys/dev/ic: rtl8169.c rtl81x9reg.h rtl81x9var.h
> 
> Log Message:
> - restructure tx descriptor handling code to decouple
>   number of tx descriptors, number of rx descriptors, and number of mbufs.
> - bump number of tx descriptors for rtl8169.  64 doesn't seem to be sufficient
>   when doing TSO.


>>+	if (sc->rtk_ldata.rtk_tx_desc_cnt >
>>+	    PAGE_SIZE / sizeof(struct rtk_desc)) {
>>+		sc->rtk_ldata.rtk_tx_desc_cnt =
>>+		    PAGE_SIZE / sizeof(struct rtk_desc);
>>+	}

Is there any reason to limit a number of TX descriptors by PAGE_SIZE?
(it's limited to 256 on 4KB/page system)

Other drivers have more descriptors, for example, tlp(4) has 1024,
and ex(4) uses >64KB DMA memory for TX descriptors.
---
Izumi Tsutsui