viaide(4): add UDMA support for VT8233C IDE controller.

The VT8233C is another obscure VIA southbridge and appears to be a variant of the
VT8233 rather than the VT8233A (which supports ATA133). The C variant was paired with
a 3Com network controller instead of VIA’s own NIC. Detect the ISA–PCI bridge and
enable UDMA100 capability for improved IDE performance.

Update the viaide(4) man page and refine the list of supported VIA controllers.

Author: vezhlys

share/man/man4/viaide.4

@@ -1,4 +1,4 @@
-.\"	$NetBSD: viaide.4,v 1.12 2025/04/21 20:37:48 andvar Exp $
+.\"	$NetBSD: viaide.4,v 1.13 2025/10/17 22:02:35 andvar Exp $
 .\"
 .\" Copyright (c) 2003 Manuel Bouyer.
 .\"
@@ -22,7 +22,7 @@
 .\" INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd April 21, 2025
+.Dd October 17, 2025
 .Dt VIAIDE 4
 .Os
 .Sh NAME
@@ -45,11 +45,11 @@ Advanced Micro Devices AMD-756, 766, 768 and CS5536 IDE Controllers
 NVIDIA nForce, nForce2, nForce2 400, nForce3, nForce3 250,
 nForce4, MCP04, MCP55, MCP61, MCP65, MCP67 IDE and SATA Controllers.
 .It
-VIA Technologies VT82C586, VT82C586A, VT82C596A, VT82C686A, VT8233A,
-VT8235, VT8237/VT8237R/VT6420, VT8237A, VT8237S, VT8251, VT8261, CX700(M/M2),
-VX700, VX800/820, VX855/875, VX900/VX11 Integrated IDE and SATA Controllers,
-VT6415/VT6330 single-channel IDE Controllers, VT6410 IDE RAID Controller, and
-VT6421 SATA RAID & IDE Controller.
+VIA Technologies VT82C586, VT82C586A, VT82C586B, VT82C596A, VT82C596B,
+VT82C686A, VT82C686B, VT8233, VT8233A, VT8233C, VT8235, VT8237/VT8237R/VT6420,
+VT8237A, VT8237S, VT8251, VT8261, CX700(M/M2), VX700, VX800/820, VX855/875,
+VX900/VX11 Integrated IDE and SATA Controllers, VT6415/VT6330 single-channel IDE
+Controllers, VT6410 IDE RAID Controller, and VT6421 SATA RAID & IDE Controller.
 .El
 .Pp
 The 0x0002 flag forces the

sys/dev/pci/viaide.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: viaide.c,v 1.104 2025/10/04 04:20:31 thorpej Exp $	*/
+/*	$NetBSD: viaide.c,v 1.105 2025/10/17 22:02:35 andvar Exp $	*/
 
 /*
  * Copyright (c) 1999, 2000, 2001 Manuel Bouyer.
@@ -26,7 +26,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: viaide.c,v 1.104 2025/10/04 04:20:31 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: viaide.c,v 1.105 2025/10/17 22:02:35 andvar Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -590,6 +590,10 @@ via_chip_map(struct pciide_softc *sc, const struct pci_attach_args *pa)
 				aprint_normal("VT8233A ATA133 controller\n");
 				sc->sc_wdcdev.sc_atac.atac_udma_cap = 6;
 				break;
+			case PCI_PRODUCT_VIATECH_VT8233C:
+				aprint_normal("VT8233C ATA100 controller\n");
+				sc->sc_wdcdev.sc_atac.atac_udma_cap = 5;
+				break;
 			case PCI_PRODUCT_VIATECH_VT8235:
 				aprint_normal("VT8235 ATA133 controller\n");
 				sc->sc_wdcdev.sc_atac.atac_udma_cap = 6;