/* * linux/drivers/char/mem.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Added devfs support. * Jan-11-1998, C. Scott Ananian * Shared /dev/zero mmaping support, Feb 2000, Kanoj Sarcar */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_IA64 # include #endif #if defined(CONFIG_S390_TAPE) && defined(CONFIG_S390_TAPE_CHAR) extern void tapechar_init(void); #endif /* * Architectures vary in how they handle caching for addresses * outside of main memory. * */ static inline int uncached_access(struct file *file, unsigned long addr) { #if defined(__i386__) /* * On the PPro and successors, the MTRRs are used to set * memory types for physical addresses outside main memory, * so blindly setting PCD or PWT on those pages is wrong. * For Pentiums and earlier, the surround logic should disable * caching for the high addresses through the KEN pin, but * we maintain the tradition of paranoia in this code. */ if (file->f_flags & O_SYNC) return 1; return !( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) || test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) || test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) || test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability) ) && addr >= __pa(high_memory); #elif defined(__x86_64__) /* * This is broken because it can generate memory type aliases, * which can cause cache corruptions * But it is only available for root and we have to be bug-to-bug * compatible with i386. */ if (file->f_flags & O_SYNC) return 1; /* same behaviour as i386. PAT always set to cached and MTRRs control the caching behaviour. Hopefully a full PAT implementation will fix that soon. */ return 0; #elif defined(CONFIG_IA64) /* * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases. */ return !(efi_mem_attributes(addr) & EFI_MEMORY_WB); #else /* * Accessing memory above the top the kernel knows about or through a file pointer * that was marked O_SYNC will be done non-cached. */ if (file->f_flags & O_SYNC) return 1; return addr >= __pa(high_memory); #endif } #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE static inline int valid_phys_addr_range(unsigned long addr, size_t *count) { unsigned long end_mem; end_mem = __pa(high_memory); if (addr >= end_mem) return 0; if (*count > end_mem - addr) *count = end_mem - addr; return 1; } #endif #ifndef ARCH_HAS_DEV_MEM /* * This funcion reads the *physical* memory. The f_pos points directly to the * memory location. */ static ssize_t read_mem(struct file * file, char __user * buf, size_t count, loff_t *ppos) { unsigned long p = *ppos; ssize_t read, sz; char *ptr; if (!valid_phys_addr_range(p, &count)) return -EFAULT; read = 0; #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED /* we don't have page 0 mapped on sparc and m68k.. */ if (p < PAGE_SIZE) { sz = PAGE_SIZE - p; if (sz > count) sz = count; if (sz > 0) { if (clear_user(buf, sz)) return -EFAULT; buf += sz; p += sz; count -= sz; read += sz; } } #endif while (count > 0) { /* * Handle first page in case it's not aligned */ if (-p & (PAGE_SIZE - 1)) sz = -p & (PAGE_SIZE - 1); else sz = PAGE_SIZE; sz = min_t(unsigned long, sz, count); /* * On ia64 if a page has been mapped somewhere as * uncached, then it must also be accessed uncached * by the kernel or data corruption may occur */ ptr = xlate_dev_mem_ptr(p); if (copy_to_user(buf, ptr, sz)) return -EFAULT; buf += sz; p += sz; count -= sz; read += sz; } *ppos += read; return read; } static ssize_t write_mem(struct file * file, const char __user * buf, size_t count, loff_t *ppos) { unsigned long p = *ppos; ssize_t written, sz; unsigned long copied; void *ptr; if (!valid_phys_addr_range(p, &count)) return -EFAULT; written = 0; #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED /* we don't have page 0 mapped on sparc and m68k.. */ if (p < PAGE_SIZE) { unsigned long sz = PAGE_SIZE - p; if (sz > count) sz = count; /* Hmm. Do something? */ buf += sz; p += sz; count -
//-----------------------------------------------------
// This is simple parity Program
// Design Name : parity
// File Name   : parity.v
// Function    : This program shows how a verilog
//               primitive/module port connection are done
// Coder       : Deepak
//-----------------------------------------------------
module parity (
a      , // First input
b      , // Second input 
c      , // Third Input
d      , // Fourth Input
y        // Parity  output
);

// Input Declaration
input       a       ;
input       b       ;
input       c       ;
input       d       ;
// Ouput Declaration
output      y      ;
// port data types
wire        a        ;
wire        b        ;
wire        c        ;
wire        d        ;
wire        y        ;
// Internal variables
wire        out_0 ;
wire        out_1 ;

// Code starts Here
xor u0 (out_0,a,b);

xor u1 (out_1,c,d);

xor u2 (y,out_0,out_1);

endmodule // End Of Module parity
generated by cgit v1.2.3 (git 2.25.1) at 2025-12-17 03:36:51 +0000
unsigned long left, unwritten, written = 0; if (!count) return 0; if (!access_ok(VERIFY_WRITE, buf, count)) return -EFAULT; left = count; /* do we want to be clever? Arbitrary cut-off */ if (count >= PAGE_SIZE*4) { unsigned long partial; /* How much left of the page? */ partial = (PAGE_SIZE-1) & -(unsigned long) buf; unwritten = clear_user(buf, partial); written = partial - unwritten; if (unwritten) goto out; left -= partial; buf += partial; unwritten = read_zero_pagealigned(buf, left & PAGE_MASK); written += (left & PAGE_MASK) - unwritten; if (unwritten) goto out; buf += left & PAGE_MASK; left &= ~PAGE_MASK; } unwritten = clear_user(buf, left); written += left - unwritten; out: return written ? written : -EFAULT; } static int mmap_zero(struct file * file, struct vm_area_struct * vma) { if (vma->vm_flags & VM_SHARED) return shmem_zero_setup(vma); if (zeromap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start, vma->vm_page_prot)) return -EAGAIN; return 0; } #else /* CONFIG_MMU */ static ssize_t read_zero(struct file * file, char * buf, size_t count, loff_t *ppos) { size_t todo = count; while (todo) { size_t chunk = todo; if (chunk > 4096) chunk = 4096; /* Just for latency reasons */ if (clear_user(buf, chunk)) return -EFAULT; buf += chunk; todo -= chunk; cond_resched(); } return count; } static int mmap_zero(struct file * file, struct vm_area_struct * vma) { return -ENOSYS; } #endif /* CONFIG_MMU */ static ssize_t write_full(struct file * file, const char __user * buf, size_t count, loff_t *ppos) { return -ENOSPC; } /* * Special lseek() function for /dev/null and /dev/zero. Most notably, you * can fopen() both devices with "a" now. This was previously impossible. * -- SRB. */ static loff_t null_lseek(struct file * file, loff_t offset, int orig) { return file->f_pos = 0; } /* * The memory devices use the full 32/64 bits of the offset, and so we cannot * check against negative addresses: they are ok. The return value is weird, * though, in that case (0). * * also note that seeking relative to the "end of file" isn't supported: * it has no meaning, so it returns -EINVAL. */ static loff_t memory_lseek(struct file * file, loff_t offset, int orig) { loff_t ret; down(&file->f_dentry->d_inode->i_sem); switch (orig) { case 0: file->f_pos = offset; ret = file->f_pos; force_successful_syscall_return(); break; case 1: file->f_pos += offset; ret = file->f_pos; force_successful_syscall_return(); break; default: ret = -EINVAL; } up(&file->f_dentry->d_inode->i_sem); return ret; } static int open_port(struct inode * inode, struct file * filp) { return capable(CAP_SYS_RAWIO) ? 0 : -EPERM; } #define zero_lseek null_lseek #define full_lseek null_lseek #define write_zero write_null #define read_full read_zero #define open_mem open_port #define open_kmem open_mem #ifndef ARCH_HAS_DEV_MEM static struct file_operations mem_fops = { .llseek = memory_lseek, .read = read_mem, .write = write_mem, .mmap = mmap_mem, .open = open_mem, }; #else extern struct file_operations mem_fops; #endif static struct file_operations kmem_fops = { .llseek = memory_lseek, .read = read_kmem, .write = write_kmem, .mmap = mmap_kmem, .open = open_kmem, }; static struct file_operations null_fops = { .llseek = null_lseek, .read = read_null, .write = write_null, }; #if defined(CONFIG_ISA) || !defined(__mc68000__) static struct file_operations port_fops = { .llseek = memory_lseek, .read = read_port, .write = write_port, .open = open_port, }; #endif static struct file_operations zero_fops = { .llseek = zero_lseek, .read = read_zero, .write = write_zero, .mmap = mmap_zero, }; static struct backing_dev_info zero_bdi = { .capabilities = BDI_CAP_MAP_COPY, }; static struct file_operations full_fops = { .llseek = full_lseek, .read = read_full, .write = write_full, }; static ssize_t kmsg_write(struct file * file, const char __user * buf, size_t count, loff_t *ppos) { char *tmp; int ret; tmp = kmalloc(count + 1, GFP_KERNEL); if (tmp == NULL) return -ENOMEM; ret = -EFAULT; if (!copy_from_user(tmp, buf, count)) { tmp[count] = 0; ret = printk("%s", tmp); } kfree(tmp); return ret; } static struct file_operations kmsg_fops = { .write = kmsg_write, }; static int memory_open(struct inode * inode, struct file * filp) { switch (iminor(inode)) { case 1: filp->f_op = &mem_fops; break; case 2: filp->f_op = &kmem_fops; break; case 3: filp->f_op = &null_fops; break; #if defined(CONFIG_ISA) || !defined(__mc68000__) case 4: filp->f_op = &port_fops; break; #endif case 5: filp->f_mapping->backing_dev_info = &zero_bdi; filp->f_op = &zero_fops; break; case 7: filp->f_op = &full_fops; break; case 8: filp->f_op = &random_fops; break; case 9: filp->f_op = &urandom_fops; break; case 11: filp->f_op = &kmsg_fops; break; default: return -ENXIO; } if (filp->f_op && filp->f_op->open) return filp->f_op->open(inode,filp); return 0; } static struct file_operations memory_fops = { .open = memory_open, /* just a selector for the real open */ }; static const struct { unsigned int minor; char *name; umode_t mode; struct file_operations *fops; } devlist[] = { /* list of minor devices */ {1, "mem", S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops}, {2, "kmem", S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops}, {3, "null", S_IRUGO | S_IWUGO, &null_fops}, #if defined(CONFIG_ISA) || !defined(__mc68000__) {4, "port", S_IRUSR | S_IWUSR | S_IRGRP, &port_fops}, #endif {5, "zero", S_IRUGO | S_IWUGO, &zero_fops}, {7, "full", S_IRUGO | S_IWUGO, &full_fops}, {8, "random", S_IRUGO | S_IWUSR, &random_fops}, {9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops}, {11,"kmsg", S_IRUGO | S_IWUSR, &kmsg_fops}, }; static struct class_simple *mem_class; static int __init chr_dev_init(void) { int i; if (register_chrdev(MEM_MAJOR,"mem",&memory_fops)) printk("unable to get major %d for memory devs\n", MEM_MAJOR); mem_class = class_simple_create(THIS_MODULE, "mem"); for (i = 0; i < ARRAY_SIZE(devlist); i++) { class_simple_device_add(mem_class, MKDEV(MEM_MAJOR, devlist[i].minor), NULL, devlist[i].name); devfs_mk_cdev(MKDEV(MEM_MAJOR, devlist[i].minor), S_IFCHR | devlist[i].mode, devlist[i].name); } return 0; } fs_initcall(chr_dev_init);