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‘Identify Device’

‘Identify Device’. A mandatory command that allows device-drivers to query any standard IDE/ATA hard disk for its parameters. Uses PIO data-in protocol. Our ‘mbr.c’ driver-module reads sector 0 using a well-documented device protocol

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‘Identify Device’

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  1. ‘Identify Device’ A mandatory command that allows device-drivers to query any standard IDE/ATA hard disk for its parameters

  2. Uses PIO data-in protocol • Our ‘mbr.c’ driver-module reads sector 0 using a well-documented device protocol • The IDENTIFY_DEVICE command (0xEC) uses the same basic protocol, except that only a 1-bit parameter is needed, to select the desired device (master=0, slave=1) • You can quickly modify our ‘mbr.c’ module to create a ‘hdid.c’ driver for disk-ID info

  3. Some items of interest • The IDENTIFY-DEVICE command returns 256 words of information (i.e., 512 bytes) • Words 10-19: Hard Disk’s Serial-Number (it consists of 20 ASCII characters) • Words 23-26: Firmware Revision Number (it consists of 8 ASCII characters) • Words 27-46: Hard Disk’s Model Number (it consists of 40 ASCII characters)

  4. Important item: disk’s capacity • Words 60-61: The total number of sectors a device-driver can access (32-bit value) • Allows for disk-capacities up to 2 terabytes (232 sectors)*(512 bytes/sect) = 241 bytes 210: 1 kilobyte = 1024 bytes 220: 1 megabyte = 1024 kilobytes 230: 1 gigabyte = 1024 megabytes 240: 1 terabyte = 1024 gigabytes

  5. C programming “hints” unsigned short idinfo[ 256 ]; unsigned long n_sectors; unsigned long long n_bytes; for (i=0; i<256; i++) idinfo[ i ] = inw( IDE_DATA ); n_sectors = *(unsigned long*)&idinfo[ 60 ]; n_bytes = 512LL * n_sectors; printf( “disk capacity: %llu bytes ”, n_bytes); printf( “(= 0x%llX bytes) \n”, n_bytes );

  6. In-class exercise #1 • Copy our ‘mbr.c’ module from the website, remame it as ‘hdid.c’, then modify a few of its lines as appropriate, so as to create a character-mode device-driver for the Hard Disk’s 256 words of device information • Use our ‘fileview’ utility to browse through this device-file (named ‘/dev/hd’), copying down the number of disk-sectors (in hex)

  7. In-class exercise #2 • Write a short C++ application program that will display these important items of Hard Disk information (in appropriate formats): • Hard Disk’s Serial Number • Firmware’s Revision Number • Hard Disk’s Model ID Number • Number of accessible sectors (hexadecimal) • Disk’s storage capacity in bytes (decimal)

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