Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932381Ab0GAAMf (ORCPT ); Wed, 30 Jun 2010 20:12:35 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:48436 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932277Ab0GAALo (ORCPT ); Wed, 30 Jun 2010 20:11:44 -0400 From: Fernando Guzman Lugo To: , Cc: , , , , Fernando Guzman Lugo Subject: [PATCH 4/9] dspbridge: remove custom mmu code from tiomap3430.c Date: Wed, 30 Jun 2010 19:20:55 -0500 Message-Id: <1277943660-4112-5-git-send-email-x0095840@ti.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <1277943660-4112-4-git-send-email-x0095840@ti.com> References: <1277943660-4112-1-git-send-email-x0095840@ti.com> <1277943660-4112-2-git-send-email-x0095840@ti.com> <1277943660-4112-3-git-send-email-x0095840@ti.com> <1277943660-4112-4-git-send-email-x0095840@ti.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 19267 Lines: 595 This patch removes all the custom mmu code remaining in tiomap3430.c which is not needed anymore. Signed-off-by: Fernando Guzman Lugo --- drivers/dsp/bridge/core/_tiomap.h | 1 - drivers/dsp/bridge/core/tiomap3430.c | 470 ---------------------------------- 2 files changed, 0 insertions(+), 471 deletions(-) diff --git a/drivers/dsp/bridge/core/_tiomap.h b/drivers/dsp/bridge/core/_tiomap.h index 4aa2358..c41fd8e 100644 --- a/drivers/dsp/bridge/core/_tiomap.h +++ b/drivers/dsp/bridge/core/_tiomap.h @@ -356,7 +356,6 @@ struct bridge_dev_context { /* TC Settings */ bool tc_word_swap_on; /* Traffic Controller Word Swap */ - struct pg_table_attrs *pt_attrs; u32 dsp_per_clks; }; diff --git a/drivers/dsp/bridge/core/tiomap3430.c b/drivers/dsp/bridge/core/tiomap3430.c index 88f5167..96cceea 100644 --- a/drivers/dsp/bridge/core/tiomap3430.c +++ b/drivers/dsp/bridge/core/tiomap3430.c @@ -105,56 +105,9 @@ static int bridge_dev_create(OUT struct bridge_dev_context static int bridge_dev_ctrl(struct bridge_dev_context *dev_context, u32 dw_cmd, IN OUT void *pargs); static int bridge_dev_destroy(struct bridge_dev_context *dev_context); -static u32 user_va2_pa(struct mm_struct *mm, u32 address); -static int pte_update(struct bridge_dev_context *hDevContext, u32 pa, - u32 va, u32 size, - struct hw_mmu_map_attrs_t *map_attrs); -static int pte_set(struct pg_table_attrs *pt, u32 pa, u32 va, - u32 size, struct hw_mmu_map_attrs_t *attrs); -static int mem_map_vmalloc(struct bridge_dev_context *hDevContext, - u32 ul_mpu_addr, u32 ulVirtAddr, - u32 ul_num_bytes, - struct hw_mmu_map_attrs_t *hw_attrs); bool wait_for_start(struct bridge_dev_context *dev_context, u32 dw_sync_addr); -/* ----------------------------------- Globals */ - -/* Attributes of L2 page tables for DSP MMU */ -struct page_info { - u32 num_entries; /* Number of valid PTEs in the L2 PT */ -}; - -/* Attributes used to manage the DSP MMU page tables */ -struct pg_table_attrs { - spinlock_t pg_lock; /* Critical section object handle */ - - u32 l1_base_pa; /* Physical address of the L1 PT */ - u32 l1_base_va; /* Virtual address of the L1 PT */ - u32 l1_size; /* Size of the L1 PT */ - u32 l1_tbl_alloc_pa; - /* Physical address of Allocated mem for L1 table. May not be aligned */ - u32 l1_tbl_alloc_va; - /* Virtual address of Allocated mem for L1 table. May not be aligned */ - u32 l1_tbl_alloc_sz; - /* Size of consistent memory allocated for L1 table. - * May not be aligned */ - - u32 l2_base_pa; /* Physical address of the L2 PT */ - u32 l2_base_va; /* Virtual address of the L2 PT */ - u32 l2_size; /* Size of the L2 PT */ - u32 l2_tbl_alloc_pa; - /* Physical address of Allocated mem for L2 table. May not be aligned */ - u32 l2_tbl_alloc_va; - /* Virtual address of Allocated mem for L2 table. May not be aligned */ - u32 l2_tbl_alloc_sz; - /* Size of consistent memory allocated for L2 table. - * May not be aligned */ - - u32 l2_num_pages; /* Number of allocated L2 PT */ - /* Array [l2_num_pages] of L2 PT info structs */ - struct page_info *pg_info; -}; /* * This Bridge driver's function interface table. @@ -210,32 +163,6 @@ static struct bridge_drv_interface drv_interface_fxns = { bridge_msg_set_queue_id, }; -static inline void tlb_flush_all(const void __iomem *base) -{ - __raw_writeb(__raw_readb(base + MMU_GFLUSH) | 1, base + MMU_GFLUSH); -} - -static inline void flush_all(struct bridge_dev_context *dev_context) -{ - if (dev_context->dw_brd_state == BRD_DSP_HIBERNATION || - dev_context->dw_brd_state == BRD_HIBERNATION) - wake_dsp(dev_context, NULL); - - tlb_flush_all(dev_context->dw_dsp_mmu_base); -} - -static void bad_page_dump(u32 pa, struct page *pg) -{ - pr_emerg("DSPBRIDGE: MAP function: COUNT 0 FOR PA 0x%x\n", pa); - pr_emerg("Bad page state in process '%s'\n" - "page:%p flags:0x%0*lx mapping:%p mapcount:%d count:%d\n" - "Backtrace:\n", - current->comm, pg, (int)(2 * sizeof(unsigned long)), - (unsigned long)pg->flags, pg->mapping, - page_mapcount(pg), page_count(pg)); - dump_stack(); -} - /* * ======== bridge_drv_entry ======== * purpose: @@ -637,7 +564,6 @@ static int bridge_brd_stop(struct bridge_dev_context *hDevContext) { int status = 0; struct bridge_dev_context *dev_context = hDevContext; - struct pg_table_attrs *pt_attrs; u32 dsp_pwr_state; int clk_status; struct dspbridge_platform_data *pdata = @@ -677,15 +603,6 @@ static int bridge_brd_stop(struct bridge_dev_context *hDevContext) dsp_wdt_enable(false); - /* This is a good place to clear the MMU page tables as well */ - if (dev_context->pt_attrs) { - pt_attrs = dev_context->pt_attrs; - memset((u8 *) pt_attrs->l1_base_va, 0x00, pt_attrs->l1_size); - memset((u8 *) pt_attrs->l2_base_va, 0x00, pt_attrs->l2_size); - memset((u8 *) pt_attrs->pg_info, 0x00, - (pt_attrs->l2_num_pages * sizeof(struct page_info))); - } - /* Reset DSP */ (*pdata->dsp_prm_rmw_bits)(OMAP3430_RST1_IVA2, OMAP3430_RST1_IVA2, OMAP3430_IVA2_MOD, RM_RSTCTRL); @@ -725,7 +642,6 @@ static int bridge_brd_delete(struct bridge_dev_context *hDevContext) { int status = 0; struct bridge_dev_context *dev_context = hDevContext; - struct pg_table_attrs *pt_attrs; int clk_status; struct dspbridge_platform_data *pdata = omap_dspbridge_dev->dev.platform_data; @@ -747,15 +663,6 @@ static int bridge_brd_delete(struct bridge_dev_context *hDevContext) dev_context->dw_brd_state = BRD_STOPPED; /* update board state */ - /* This is a good place to clear the MMU page tables as well */ - if (dev_context->pt_attrs) { - pt_attrs = dev_context->pt_attrs; - memset((u8 *) pt_attrs->l1_base_va, 0x00, pt_attrs->l1_size); - memset((u8 *) pt_attrs->l2_base_va, 0x00, pt_attrs->l2_size); - memset((u8 *) pt_attrs->pg_info, 0x00, - (pt_attrs->l2_num_pages * sizeof(struct page_info))); - } - /* Reset DSP */ (*pdata->dsp_prm_rmw_bits)(OMAP3430_RST1_IVA2, OMAP3430_RST1_IVA2, OMAP3430_IVA2_MOD, RM_RSTCTRL); @@ -836,10 +743,6 @@ static int bridge_dev_create(OUT struct bridge_dev_context struct bridge_dev_context *dev_context = NULL; s32 entry_ndx; struct cfg_hostres *resources = pConfig; - struct pg_table_attrs *pt_attrs; - u32 pg_tbl_pa; - u32 pg_tbl_va; - u32 align_size; struct drv_data *drv_datap = dev_get_drvdata(bridge); /* Allocate and initialize a data structure to contain the bridge driver @@ -871,97 +774,11 @@ static int bridge_dev_create(OUT struct bridge_dev_context if (!dev_context->dw_dsp_base_addr) status = -EPERM; - pt_attrs = kzalloc(sizeof(struct pg_table_attrs), GFP_KERNEL); - if (pt_attrs != NULL) { - /* Assuming that we use only DSP's memory map - * until 0x4000:0000 , we would need only 1024 - * L1 enties i.e L1 size = 4K */ - pt_attrs->l1_size = 0x1000; - align_size = pt_attrs->l1_size; - /* Align sizes are expected to be power of 2 */ - /* we like to get aligned on L1 table size */ - pg_tbl_va = (u32) mem_alloc_phys_mem(pt_attrs->l1_size, - align_size, &pg_tbl_pa); - - /* Check if the PA is aligned for us */ - if ((pg_tbl_pa) & (align_size - 1)) { - /* PA not aligned to page table size , - * try with more allocation and align */ - mem_free_phys_mem((void *)pg_tbl_va, pg_tbl_pa, - pt_attrs->l1_size); - /* we like to get aligned on L1 table size */ - pg_tbl_va = - (u32) mem_alloc_phys_mem((pt_attrs->l1_size) * 2, - align_size, &pg_tbl_pa); - /* We should be able to get aligned table now */ - pt_attrs->l1_tbl_alloc_pa = pg_tbl_pa; - pt_attrs->l1_tbl_alloc_va = pg_tbl_va; - pt_attrs->l1_tbl_alloc_sz = pt_attrs->l1_size * 2; - /* Align the PA to the next 'align' boundary */ - pt_attrs->l1_base_pa = - ((pg_tbl_pa) + - (align_size - 1)) & (~(align_size - 1)); - pt_attrs->l1_base_va = - pg_tbl_va + (pt_attrs->l1_base_pa - pg_tbl_pa); - } else { - /* We got aligned PA, cool */ - pt_attrs->l1_tbl_alloc_pa = pg_tbl_pa; - pt_attrs->l1_tbl_alloc_va = pg_tbl_va; - pt_attrs->l1_tbl_alloc_sz = pt_attrs->l1_size; - pt_attrs->l1_base_pa = pg_tbl_pa; - pt_attrs->l1_base_va = pg_tbl_va; - } - if (pt_attrs->l1_base_va) - memset((u8 *) pt_attrs->l1_base_va, 0x00, - pt_attrs->l1_size); - - /* number of L2 page tables = DMM pool used + SHMMEM +EXTMEM + - * L4 pages */ - pt_attrs->l2_num_pages = ((DMMPOOLSIZE >> 20) + 6); - pt_attrs->l2_size = HW_MMU_COARSE_PAGE_SIZE * - pt_attrs->l2_num_pages; - align_size = 4; /* Make it u32 aligned */ - /* we like to get aligned on L1 table size */ - pg_tbl_va = (u32) mem_alloc_phys_mem(pt_attrs->l2_size, - align_size, &pg_tbl_pa); - pt_attrs->l2_tbl_alloc_pa = pg_tbl_pa; - pt_attrs->l2_tbl_alloc_va = pg_tbl_va; - pt_attrs->l2_tbl_alloc_sz = pt_attrs->l2_size; - pt_attrs->l2_base_pa = pg_tbl_pa; - pt_attrs->l2_base_va = pg_tbl_va; - - if (pt_attrs->l2_base_va) - memset((u8 *) pt_attrs->l2_base_va, 0x00, - pt_attrs->l2_size); - - pt_attrs->pg_info = kzalloc(pt_attrs->l2_num_pages * - sizeof(struct page_info), GFP_KERNEL); - dev_dbg(bridge, - "L1 pa %x, va %x, size %x\n L2 pa %x, va " - "%x, size %x\n", pt_attrs->l1_base_pa, - pt_attrs->l1_base_va, pt_attrs->l1_size, - pt_attrs->l2_base_pa, pt_attrs->l2_base_va, - pt_attrs->l2_size); - dev_dbg(bridge, "pt_attrs %p L2 NumPages %x pg_info %p\n", - pt_attrs, pt_attrs->l2_num_pages, pt_attrs->pg_info); - } - if ((pt_attrs != NULL) && (pt_attrs->l1_base_va != 0) && - (pt_attrs->l2_base_va != 0) && (pt_attrs->pg_info != NULL)) - dev_context->pt_attrs = pt_attrs; - else - status = -ENOMEM; - if (DSP_SUCCEEDED(status)) { - spin_lock_init(&pt_attrs->pg_lock); dev_context->tc_word_swap_on = drv_datap->tc_wordswapon; - - /* Set the Clock Divisor for the DSP module */ - udelay(5); /* MMU address is obtained from the host * resources struct */ dev_context->dw_dsp_mmu_base = resources->dw_dmmu_base; - } - if (DSP_SUCCEEDED(status)) { dev_context->hdev_obj = hdev_obj; dev_context->ul_int_mask = 0; /* Store current board state. */ @@ -970,23 +787,6 @@ static int bridge_dev_create(OUT struct bridge_dev_context /* Return ptr to our device state to the DSP API for storage */ *ppDevContext = dev_context; } else { - if (pt_attrs != NULL) { - kfree(pt_attrs->pg_info); - - if (pt_attrs->l2_tbl_alloc_va) { - mem_free_phys_mem((void *) - pt_attrs->l2_tbl_alloc_va, - pt_attrs->l2_tbl_alloc_pa, - pt_attrs->l2_tbl_alloc_sz); - } - if (pt_attrs->l1_tbl_alloc_va) { - mem_free_phys_mem((void *) - pt_attrs->l1_tbl_alloc_va, - pt_attrs->l1_tbl_alloc_pa, - pt_attrs->l1_tbl_alloc_sz); - } - } - kfree(pt_attrs); kfree(dev_context); } func_end: @@ -1054,7 +854,6 @@ static int bridge_dev_ctrl(struct bridge_dev_context *dev_context, */ static int bridge_dev_destroy(struct bridge_dev_context *hDevContext) { - struct pg_table_attrs *pt_attrs; int status = 0; struct bridge_dev_context *dev_context = (struct bridge_dev_context *) hDevContext; @@ -1068,23 +867,6 @@ static int bridge_dev_destroy(struct bridge_dev_context *hDevContext) /* first put the device to stop state */ bridge_brd_delete(dev_context); - if (dev_context->pt_attrs) { - pt_attrs = dev_context->pt_attrs; - kfree(pt_attrs->pg_info); - - if (pt_attrs->l2_tbl_alloc_va) { - mem_free_phys_mem((void *)pt_attrs->l2_tbl_alloc_va, - pt_attrs->l2_tbl_alloc_pa, - pt_attrs->l2_tbl_alloc_sz); - } - if (pt_attrs->l1_tbl_alloc_va) { - mem_free_phys_mem((void *)pt_attrs->l1_tbl_alloc_va, - pt_attrs->l1_tbl_alloc_pa, - pt_attrs->l1_tbl_alloc_sz); - } - kfree(pt_attrs); - - } if (dev_context->resources) { host_res = dev_context->resources; @@ -1315,258 +1097,6 @@ int user_to_dsp_unmap(struct iommu *mmu, u32 da) } /* - * ======== user_va2_pa ======== - * Purpose: - * This function walks through the page tables to convert a userland - * virtual address to physical address - */ -static u32 user_va2_pa(struct mm_struct *mm, u32 address) -{ - pgd_t *pgd; - pmd_t *pmd; - pte_t *ptep, pte; - - pgd = pgd_offset(mm, address); - if (!(pgd_none(*pgd) || pgd_bad(*pgd))) { - pmd = pmd_offset(pgd, address); - if (!(pmd_none(*pmd) || pmd_bad(*pmd))) { - ptep = pte_offset_map(pmd, address); - if (ptep) { - pte = *ptep; - if (pte_present(pte)) - return pte & PAGE_MASK; - } - } - } - - return 0; -} - -/* - * ======== pte_update ======== - * This function calculates the optimum page-aligned addresses and sizes - * Caller must pass page-aligned values - */ -static int pte_update(struct bridge_dev_context *hDevContext, u32 pa, - u32 va, u32 size, - struct hw_mmu_map_attrs_t *map_attrs) -{ - u32 i; - u32 all_bits; - u32 pa_curr = pa; - u32 va_curr = va; - u32 num_bytes = size; - struct bridge_dev_context *dev_context = hDevContext; - int status = 0; - u32 page_size[] = { HW_PAGE_SIZE16MB, HW_PAGE_SIZE1MB, - HW_PAGE_SIZE64KB, HW_PAGE_SIZE4KB - }; - - while (num_bytes && DSP_SUCCEEDED(status)) { - /* To find the max. page size with which both PA & VA are - * aligned */ - all_bits = pa_curr | va_curr; - - for (i = 0; i < 4; i++) { - if ((num_bytes >= page_size[i]) && ((all_bits & - (page_size[i] - - 1)) == 0)) { - status = - pte_set(dev_context->pt_attrs, pa_curr, - va_curr, page_size[i], map_attrs); - pa_curr += page_size[i]; - va_curr += page_size[i]; - num_bytes -= page_size[i]; - /* Don't try smaller sizes. Hopefully we have - * reached an address aligned to a bigger page - * size */ - break; - } - } - } - - return status; -} - -/* - * ======== pte_set ======== - * This function calculates PTE address (MPU virtual) to be updated - * It also manages the L2 page tables - */ -static int pte_set(struct pg_table_attrs *pt, u32 pa, u32 va, - u32 size, struct hw_mmu_map_attrs_t *attrs) -{ - u32 i; - u32 pte_val; - u32 pte_addr_l1; - u32 pte_size; - /* Base address of the PT that will be updated */ - u32 pg_tbl_va; - u32 l1_base_va; - /* Compiler warns that the next three variables might be used - * uninitialized in this function. Doesn't seem so. Working around, - * anyways. */ - u32 l2_base_va = 0; - u32 l2_base_pa = 0; - u32 l2_page_num = 0; - int status = 0; - - l1_base_va = pt->l1_base_va; - pg_tbl_va = l1_base_va; - if ((size == HW_PAGE_SIZE64KB) || (size == HW_PAGE_SIZE4KB)) { - /* Find whether the L1 PTE points to a valid L2 PT */ - pte_addr_l1 = hw_mmu_pte_addr_l1(l1_base_va, va); - if (pte_addr_l1 <= (pt->l1_base_va + pt->l1_size)) { - pte_val = *(u32 *) pte_addr_l1; - pte_size = hw_mmu_pte_size_l1(pte_val); - } else { - return -EPERM; - } - spin_lock(&pt->pg_lock); - if (pte_size == HW_MMU_COARSE_PAGE_SIZE) { - /* Get the L2 PA from the L1 PTE, and find - * corresponding L2 VA */ - l2_base_pa = hw_mmu_pte_coarse_l1(pte_val); - l2_base_va = - l2_base_pa - pt->l2_base_pa + pt->l2_base_va; - l2_page_num = - (l2_base_pa - - pt->l2_base_pa) / HW_MMU_COARSE_PAGE_SIZE; - } else if (pte_size == 0) { - /* L1 PTE is invalid. Allocate a L2 PT and - * point the L1 PTE to it */ - /* Find a free L2 PT. */ - for (i = 0; (i < pt->l2_num_pages) && - (pt->pg_info[i].num_entries != 0); i++) - ;; - if (i < pt->l2_num_pages) { - l2_page_num = i; - l2_base_pa = pt->l2_base_pa + (l2_page_num * - HW_MMU_COARSE_PAGE_SIZE); - l2_base_va = pt->l2_base_va + (l2_page_num * - HW_MMU_COARSE_PAGE_SIZE); - /* Endianness attributes are ignored for - * HW_MMU_COARSE_PAGE_SIZE */ - status = - hw_mmu_pte_set(l1_base_va, l2_base_pa, va, - HW_MMU_COARSE_PAGE_SIZE, - attrs); - } else { - status = -ENOMEM; - } - } else { - /* Found valid L1 PTE of another size. - * Should not overwrite it. */ - status = -EPERM; - } - if (DSP_SUCCEEDED(status)) { - pg_tbl_va = l2_base_va; - if (size == HW_PAGE_SIZE64KB) - pt->pg_info[l2_page_num].num_entries += 16; - else - pt->pg_info[l2_page_num].num_entries++; - dev_dbg(bridge, "PTE: L2 BaseVa %x, BasePa %x, PageNum " - "%x, num_entries %x\n", l2_base_va, - l2_base_pa, l2_page_num, - pt->pg_info[l2_page_num].num_entries); - } - spin_unlock(&pt->pg_lock); - } - if (DSP_SUCCEEDED(status)) { - dev_dbg(bridge, "PTE: pg_tbl_va %x, pa %x, va %x, size %x\n", - pg_tbl_va, pa, va, size); - dev_dbg(bridge, "PTE: endianism %x, element_size %x, " - "mixed_size %x\n", attrs->endianism, - attrs->element_size, attrs->mixed_size); - status = hw_mmu_pte_set(pg_tbl_va, pa, va, size, attrs); - } - - return status; -} - -/* Memory map kernel VA -- memory allocated with vmalloc */ -static int mem_map_vmalloc(struct bridge_dev_context *dev_context, - u32 ul_mpu_addr, u32 ulVirtAddr, - u32 ul_num_bytes, - struct hw_mmu_map_attrs_t *hw_attrs) -{ - int status = 0; - struct page *page[1]; - u32 i; - u32 pa_curr; - u32 pa_next; - u32 va_curr; - u32 size_curr; - u32 num_pages; - u32 pa; - u32 num_of4k_pages; - u32 temp = 0; - - /* - * Do Kernel va to pa translation. - * Combine physically contiguous regions to reduce TLBs. - * Pass the translated pa to pte_update. - */ - num_pages = ul_num_bytes / PAGE_SIZE; /* PAGE_SIZE = OS page size */ - i = 0; - va_curr = ul_mpu_addr; - page[0] = vmalloc_to_page((void *)va_curr); - pa_next = page_to_phys(page[0]); - while (DSP_SUCCEEDED(status) && (i < num_pages)) { - /* - * Reuse pa_next from the previous iteraion to avoid - * an extra va2pa call - */ - pa_curr = pa_next; - size_curr = PAGE_SIZE; - /* - * If the next page is physically contiguous, - * map it with the current one by increasing - * the size of the region to be mapped - */ - while (++i < num_pages) { - page[0] = - vmalloc_to_page((void *)(va_curr + size_curr)); - pa_next = page_to_phys(page[0]); - - if (pa_next == (pa_curr + size_curr)) - size_curr += PAGE_SIZE; - else - break; - - } - if (pa_next == 0) { - status = -ENOMEM; - break; - } - pa = pa_curr; - num_of4k_pages = size_curr / HW_PAGE_SIZE4KB; - while (temp++ < num_of4k_pages) { - get_page(PHYS_TO_PAGE(pa)); - pa += HW_PAGE_SIZE4KB; - } - status = pte_update(dev_context, pa_curr, ulVirtAddr + - (va_curr - ul_mpu_addr), size_curr, - hw_attrs); - va_curr += size_curr; - } - if (DSP_SUCCEEDED(status)) - status = 0; - else - status = -EPERM; - - /* - * In any case, flush the TLB - * This is called from here instead from pte_update to avoid unnecessary - * repetition while mapping non-contiguous physical regions of a virtual - * region - */ - flush_all(dev_context); - dev_dbg(bridge, "%s status %x\n", __func__, status); - return status; -} - -/* * ======== wait_for_start ======== * Wait for the singal from DSP that it has started, or time out. */ -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/