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Pstore dmesg read篇

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当系统重启后，可以把数据从pstore中读出来，并创建文件节点，提供用户接口来获取文本数据。

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static int ramoops_probe(struct platform_device * pdev)
{
	/* 从pstore中取出数据 */
	err = ramoops_init_przs(dev, cxt, &paddr, dump_mem_sz);
	
	/* 写入文件节点 */
	err = pstore_register(&cxt->pstore);
}

  1. 读取数据

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    static int ramoops_init_przs(struct device * dev, struct ramoops_context cxt,
    				phys_addr_t * paddr, size_t dump_mem_sz)
    {
    	for (i = 0; i < cxt->max_dump_cnt; i++) {
    		cxt->przs[i] = persistent_ram_new(*paddr, cxt->record_size, 0,
    							&cxt->ecc_info,
    							cxt->memtype, 0);
    		*paddr += cxt->record_size;
    	}
    	return 0;
    }
     
    struct persistent_ram_zone * persistent_ram_new(phys_addr_t start, size_t size,
    			u32 sig, struct persistent_ram_ecc_info * ecc_info,
    			unsigned int memtype, u32 flags)
    {
    	struct persistent_ram_zone * prz;
    	
    	ret = persistent_ram_post_init(prz, sig, ecc_info);
    	return ERR_PTR(ret);
    }
     
    static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
    					struct persistent_ram_ecc_info * ecc_info)
    {
    	/* 通过魔术字判断是否有dump数据 */
    	sig ^= PERSISTENT_RAM_SIG;
    	
    	if (prz->buffer->sig == sig) {
    		persistent_ram_save_old(prz);
    	}
    	
    	prz->buffer->sig = sig;
    	
    	return 0;
    }
     
    void persistent_ram_save_old(struct persistent_ram_zone * prz)
    {
    	struct persistent_ram_buffer * buffer = prz->buffer;
    	size_t size  = buffer_size(prz);
    	size_t start = buffer_start(prz);
    	
    	prz->old_log_size = size;
    	/* 环形缓冲区，start是起点 */
    	memcpy_fromio(prz->old, &buffer->data[start], size - start);
    	memcpy_fromio(prz->old_log + size -start, &buffer->data[0], start);
    	
    }

  1. 创建文件节点，提供用户接口

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    int pstore_register(struct pstore_info * psi)
    {
    	if (pstore_is_mounted())
    		pstore_get_records(0);
    }
     
    void pstore_get_records(int quiet)
    {
    	while ((size = psi->read(&id, &type, &count, &time, &buf, &compressed,
    				psi)) > 0) {
    		if (compressed && (type == PSTORE_TYPE_DMESG)) {
    			if (big_oops_buf)
    				/* 解压 */
    				unzipped_len = pstore_decompress(buf,
    							big_oops_buf, size,
    							big_oops_buf_sz);			
    		}
    		
    		/* 创建文件节点 */
    		rc = pstore_mkfile(type, psi->name, id, count, buf,
    					compressed, (size_t)size, time, psi);
    					
    	}
    }