kernel/amd64: bus: Add bus resource interface

This commit introduces a bus resource abstraction. A bus resource
encapsulates bus specific information and semantics. Along with
abstracting away bus specific details and providing an overall
smoother interface, this additionally provides flexibility, access
control and security by keeping track of permissions and allowing
things to be turned on or off.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 233 insertions, 0 deletions

diff --git a/sys/arch/amd64/amd64/bus_machdep.c b/sys/arch/amd64/amd64/bus_machdep.c
index d542821..89ef317 100644
--- a/sys/arch/amd64/amd64/bus_machdep.c
+++ b/sys/arch/amd64/amd64/bus_machdep.c
@@ -34,6 +34,52 @@
 #include <vm/vm.h>
 #include <vm/map.h>
 #include <vm/pmap.h>
+#include <vm/dynalloc.h>
+#include <dev/pci/resource.h>
+#include <string.h>
+
+#define BUS_PCI "PCI"
+#define BUS_LPC "LPC"
+
+/*
+ * Set bus specific fields
+ *
+ * @brp: Bus resource pointer.
+ * @type: Bus name/signature
+ *
+ * XXX: Assumes brp->base has already been set to
+ *      a valid bus address.
+ */
+static int
+bus_set(struct bus_resource *brp, const char *type)
+{
+    struct bus_op *io = &brp->io;
+
+    switch (*type) {
+    case 'P':
+        if (strcmp(type, BUS_PCI) == 0) {
+            /*
+             * Bus addresses for 64-bit PCI can theoretically
+             * span 2^64 bytes (i.e., the full 64-bit address space)
+             */
+            brp->dma_max = (bus_addr_t)-1;
+            brp->dma_min = 0;
+
+            /* Set hooks */
+            io->enable_dma = pcir_enable_dma;
+            io->disable_dma = pcir_disable_dma;
+            io->set_sem = pcir_set_sem;
+            io->clr_sem = pcir_clr_sem;
+            io->dma_alloc = pcir_dma_alloc;
+            io->dma_free = pcir_dma_free;
+            io->dma_in = pcir_dma_in;
+            io->dma_out = pcir_dma_out;
+            return 0;
+        }
+    }
+
+    return -ENODEV;
+}
 
 /*
  * Map a physical device address into the kernel address
@@ -78,3 +124,31 @@ bus_map(bus_addr_t addr, size_t size, int flags, void **vap)
     *vap = (void *)va;
     return 0;
 }
+
+/*
+ * Associate a specific bus with a 'bus_resource`
+ * structure.
+ *
+ * @name: Signature.
+ */
+struct bus_resource *
+bus_establish(const char *name)
+{
+    struct bus_resource *brp;
+    size_t siglen;
+
+    siglen = strlen(name);
+    if (siglen > RSIG_MAX) {
+        return NULL;
+    }
+
+    /* Allocate a new bus resource handle */
+    if ((brp = dynalloc(sizeof(*brp))) == NULL) {
+        return NULL;
+    }
+
+    memset(brp, 0, sizeof(*brp));
+    memcpy(brp->signature, name, siglen);
+    bus_set(brp, name);
+    return brp;
+}
diff --git a/sys/arch/amd64/pci/pci_resource.c b/sys/arch/amd64/pci/pci_resource.c
new file mode 100644
index 0000000..5ca597b
--- /dev/null
+++ b/sys/arch/amd64/pci/pci_resource.c
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/errno.h>
+#include <sys/syslog.h>
+#include <dev/pci/resource.h>
+#include <dev/pci/pci.h>
+#include <dev/pci/pciregs.h>
+
+// #define DEBUG 1
+
+#define pr_trace(fmt, ...) kprintf("pci: " fmt, ##__VA_ARGS__)
+#define pr_error(...) pr_trace(__VA_ARGS__)
+
+#if defined(DEBUG)
+#define pr_debug(...) pr_trace(__VA_ARGS__)
+#else
+#define pr_debug(...) __nothing
+#endif
+
+/*
+ * Enables bus mastering for a specific PCI device.
+ *
+ * @brp: Pointer to bus resource handle.
+ * @devp: Pointer to `pci_device' structure.
+ *
+ * XXX: If the bus resource is MMIO capable, PCI
+ *      memory space access will become set within
+ *      the command/status register
+ */
+int
+pcir_enable_dma(struct bus_resource *brp, void *devp)
+{
+    struct pci_device *dev = devp;
+    uint32_t tmp;
+
+    if (brp == NULL || dev == NULL) {
+        return -EINVAL;
+    }
+
+    /*
+     * Make sure that we are allowed to perform DMA. This
+     * will fail if the bus isn't DMA-capable or if DMA
+     * is disabled.
+     */
+    if (!ISSET(brp->sem, BUS_DMA)) {
+        pr_trace("Bus marked non DMA capable, DMA not enabled\n");
+        return -EACCES;
+    }
+
+    tmp = pci_readl(dev, PCIREG_CMDSTATUS);
+    tmp |= PCI_BUS_MASTERING;
+    tmp |= ISSET(brp->sem, BUS_MMIO);
+    pci_writel(dev, PCIREG_CMDSTATUS, tmp);
+    return 0;
+}
+
+/*
+ * Disables bus mastering for a specific PCI device.
+ *
+ * @brp: Pointer to bus resource handle.
+ * @devp: Pointer to `pci_device' structure.
+ *
+ * XXX: If the bus resource is not MMIO capable, PCI
+ *      memory space access will become unset within
+ *      the command/status register
+ */
+int
+pcir_disable_dma(struct bus_resource *brp, void *devp)
+{
+    struct pci_device *dev = devp;
+    uint32_t tmp;
+
+    if (brp == NULL || dev == NULL) {
+        return -EINVAL;
+    }
+
+    tmp = pci_readl(dev, PCIREG_CMDSTATUS);
+    tmp &= ~PCI_BUS_MASTERING;
+    tmp &= ~ISSET(brp->sem, BUS_MMIO);
+    pci_writel(dev, PCIREG_CMDSTATUS, tmp);
+    return 0;
+}
+
+int
+pcir_set_sem(struct bus_resource *brp, bus_sem_t sem)
+{
+    /*
+     * BUS_PIO and BUS_MMIO are two different things
+     * and must be mutually exclusive...
+     */
+    if (ISSET(sem, BUS_MMIO) && ISSET(sem, BUS_PIO)) {
+        pr_debug("Bad semantics (sem=%x)\n", sem);
+        return -EINVAL;
+    }
+
+    brp->sem |= sem;
+    return 0;
+}
+
+int
+pcir_clr_sem(struct bus_resource *brp, bus_sem_t sem)
+{
+    brp->sem &= ~sem;
+    return 0;
+}
+
+__unused int
+pcir_dma_alloc(struct bus_resource *brp, void *res)
+{
+    return 0;
+}
+
+__unused int
+pcir_dma_free(struct bus_resource *brp, void *p)
+{
+    return 0;
+}
+
+ssize_t
+pcir_dma_in(struct bus_resource *brp, void *p)
+{
+    return 0;
+}
+
+ssize_t
+pcir_dma_out(struct bus_resource *brp, void *p)
+{
+    return 0;
+}