The NetBSD driver sometimes uses commands without DMA (for example a simple TEST_UNIT_READY). On esp hardware, the command has a DMA bit (if dma is to be used), and when writing to the command register, the s->dma status is updated accordingly.
When commands with dma are used and dma is disabled, the command is defered untill dma is enabled again. This is all fine. However, the deferal should not happen if the command does not use dma. This can bee seen by booting NetBSD/sparc: for every scsi device attached there will be a 5 second timeout and an error message. Here is a trivial patch wich fixes this problem for me: --- hw/esp.c.orig 2012-06-01 11:13:13.000000000 +0200 +++ hw/esp.c 2012-06-18 01:43:34.000000000 +0200 @@ -270,7 +270,7 @@ static void handle_satn(ESPState *s) uint8_t buf[32]; int len; - if (!s->dma_enabled) { + if (s->dma && !s->dma_enabled) { s->dma_cb = handle_satn; return; } @@ -284,7 +284,7 @@ static void handle_s_without_atn(ESPStat uint8_t buf[32]; int len; - if (!s->dma_enabled) { + if (s->dma && !s->dma_enabled) { s->dma_cb = handle_s_without_atn; return; } @@ -296,7 +296,7 @@ static void handle_s_without_atn(ESPStat static void handle_satn_stop(ESPState *s) { - if (!s->dma_enabled) { + if (s->dma && !s->dma_enabled) { s->dma_cb = handle_satn_stop; return; } I filed a ticket in the bugtracker for it: #1014099. Martin