From: Tulio A M Mendes <tadryanom@hotmail.com>
Date: Thu, 12 Feb 2026 04:36:43 +0000 (-0300)
Subject: feat: zero-copy DMA I/O — ata_dma_read_direct/ata_dma_write_direct bypass bounce... 
X-Git-Url: https://projects.tadryanom.me/?a=commitdiff_plain;h=d23c85ecd32a6b732ebe3c986bc6fe19d6be7015;p=AdrOS.git

feat: zero-copy DMA I/O — ata_dma_read_direct/ata_dma_write_direct bypass bounce buffer with caller-provided physical address
---

diff --git a/include/ata_dma.h b/include/ata_dma.h
index 5f4b384..fef3b47 100644
--- a/include/ata_dma.h
+++ b/include/ata_dma.h
@@ -20,4 +20,10 @@ int ata_dma_read28(uint32_t lba, uint8_t* buf512);
  * Returns 0 on success, negative errno on failure. */
 int ata_dma_write28(uint32_t lba, const uint8_t* buf512);
 
+/* Zero-copy DMA: read/write using a caller-provided physical address.
+ * phys_buf must be 32-bit aligned, below 4GB, and not cross a 64KB boundary.
+ * Returns 0 on success, negative errno on failure. */
+int ata_dma_read_direct(uint32_t lba, uint32_t phys_buf, uint16_t byte_count);
+int ata_dma_write_direct(uint32_t lba, uint32_t phys_buf, uint16_t byte_count);
+
 #endif
diff --git a/src/hal/x86/ata_dma.c b/src/hal/x86/ata_dma.c
index 6d87fa6..aeb8ce0 100644
--- a/src/hal/x86/ata_dma.c
+++ b/src/hal/x86/ata_dma.c
@@ -312,3 +312,52 @@ int ata_dma_write28(uint32_t lba, const uint8_t* buf512) {
     spin_unlock(&dma_lock);
     return ret;
 }
+
+int ata_dma_read_direct(uint32_t lba, uint32_t phys_buf, uint16_t byte_count) {
+    if (!dma_available) return -ENOSYS;
+    if (phys_buf == 0 || (phys_buf & 1)) return -EINVAL;
+    if (byte_count == 0) byte_count = 512;
+
+    spin_lock(&dma_lock);
+
+    /* Save original PRDT and reprogram for zero-copy */
+    uint32_t saved_addr = prdt[0].phys_addr;
+    uint16_t saved_count = prdt[0].byte_count;
+    prdt[0].phys_addr = phys_buf;
+    prdt[0].byte_count = byte_count;
+
+    int ret = ata_dma_transfer(lba, 0);
+
+    /* Restore original PRDT for bounce-buffer mode */
+    prdt[0].phys_addr = saved_addr;
+    prdt[0].byte_count = saved_count;
+
+    spin_unlock(&dma_lock);
+    return ret;
+}
+
+int ata_dma_write_direct(uint32_t lba, uint32_t phys_buf, uint16_t byte_count) {
+    if (!dma_available) return -ENOSYS;
+    if (phys_buf == 0 || (phys_buf & 1)) return -EINVAL;
+    if (byte_count == 0) byte_count = 512;
+
+    spin_lock(&dma_lock);
+
+    uint32_t saved_addr = prdt[0].phys_addr;
+    uint16_t saved_count = prdt[0].byte_count;
+    prdt[0].phys_addr = phys_buf;
+    prdt[0].byte_count = byte_count;
+
+    int ret = ata_dma_transfer(lba, 1);
+
+    if (ret == 0) {
+        outb((uint16_t)(ATA_IO_BASE + ATA_REG_COMMAND), ATA_CMD_CACHE_FLUSH);
+        (void)ata_wait_not_busy();
+    }
+
+    prdt[0].phys_addr = saved_addr;
+    prdt[0].byte_count = saved_count;
+
+    spin_unlock(&dma_lock);
+    return ret;
+}