Add IDE/ATA disk driver with devicefs integration

Implement PIO-mode IDE driver that scans primary and secondary channels
for ATA hard drives and ATAPI CD/DVD drives using IDENTIFY commands.

Features:
- Scans 4 possible devices (2 channels x 2 drives each)
- ATA IDENTIFY DEVICE for hard drives
- ATAPI IDENTIFY PACKET DEVICE for CD/DVD drives
- PIO-mode 28-bit LBA sector read/write for ATA drives
- Model string extraction and sector count parsing
- Registers as kernel driver via REGISTER_DRIVER macro
- Registers devices with devicefs: ATA → hdd class, ATAPI → cd class
- Added inw/outw to port_io.h for 16-bit I/O

Tested: QEMU detects hdd1 (QEMU HARDDISK) and cd1 (QEMU DVD-ROM).

src/ide.h

@@ -0,0 +1,88 @@
+/**
+ * @file ide.h
+ * @brief IDE/ATA disk driver.
+ *
+ * Enumerates IDE devices on the primary and secondary channels, identifies
+ * ATA hard drives and ATAPI CD-ROMs, and registers them with the devicefs
+ * subsystem as block devices (hddN / cdN).
+ */
+
+#ifndef IDE_H
+#define IDE_H
+
+#include <stdint.h>
+
+/** Maximum number of IDE devices (2 channels × 2 drives). */
+#define IDE_MAX_DEVICES 4
+
+/** IDE channel I/O port bases. */
+#define IDE_PRIMARY_IO     0x1F0
+#define IDE_PRIMARY_CTRL   0x3F6
+#define IDE_SECONDARY_IO   0x170
+#define IDE_SECONDARY_CTRL 0x376
+
+/** IDE register offsets from I/O base. */
+#define IDE_REG_DATA       0x00
+#define IDE_REG_ERROR      0x01
+#define IDE_REG_FEATURES   0x01
+#define IDE_REG_SECCOUNT   0x02
+#define IDE_REG_LBA_LO     0x03
+#define IDE_REG_LBA_MID    0x04
+#define IDE_REG_LBA_HI     0x05
+#define IDE_REG_DRIVE_HEAD 0x06
+#define IDE_REG_STATUS     0x07
+#define IDE_REG_COMMAND    0x07
+
+/** IDE status register bits. */
+#define IDE_STATUS_ERR   0x01  /**< Error occurred. */
+#define IDE_STATUS_DRQ   0x08  /**< Data request ready. */
+#define IDE_STATUS_SRV   0x10  /**< Overlapped mode service request. */
+#define IDE_STATUS_DF    0x20  /**< Drive fault. */
+#define IDE_STATUS_DRDY  0x40  /**< Drive ready. */
+#define IDE_STATUS_BSY   0x80  /**< Drive busy. */
+
+/** IDE commands. */
+#define IDE_CMD_IDENTIFY     0xEC  /**< ATA IDENTIFY DEVICE. */
+#define IDE_CMD_IDENTIFY_PKT 0xA1  /**< ATAPI IDENTIFY PACKET DEVICE. */
+#define IDE_CMD_READ_PIO     0x20  /**< Read sectors (PIO, 28-bit LBA). */
+#define IDE_CMD_WRITE_PIO    0x30  /**< Write sectors (PIO, 28-bit LBA). */
+
+/** IDE device types. */
+#define IDE_TYPE_NONE  0  /**< No device present. */
+#define IDE_TYPE_ATA   1  /**< ATA hard disk. */
+#define IDE_TYPE_ATAPI 2  /**< ATAPI CD/DVD drive. */
+
+/**
+ * IDE device descriptor.
+ */
+typedef struct ide_device {
+    uint8_t present;            /**< 1 if device is present. */
+    uint8_t type;               /**< IDE_TYPE_ATA or IDE_TYPE_ATAPI. */
+    uint8_t channel;            /**< 0 = primary, 1 = secondary. */
+    uint8_t drive;              /**< 0 = master, 1 = slave. */
+    uint16_t io_base;           /**< I/O base port for this channel. */
+    uint16_t ctrl_base;         /**< Control port for this channel. */
+    uint32_t sector_count;      /**< Total sectors (28-bit LBA max). */
+    uint32_t sector_size;       /**< Sector size in bytes (usually 512). */
+    char model[41];             /**< Model string from IDENTIFY. */
+} ide_device_t;
+
+/**
+ * Initialize the IDE driver.
+ *
+ * Scans primary and secondary channels for ATA/ATAPI devices,
+ * reads their IDENTIFY data, and registers them with devicefs.
+ *
+ * @return Number of devices found.
+ */
+int ide_init(void);
+
+/**
+ * Get an IDE device by index (0–3).
+ *
+ * @param index Device index.
+ * @return Pointer to the device descriptor, or NULL if invalid/not present.
+ */
+ide_device_t *ide_get_device(int index);
+
+#endif /* IDE_H */