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	 > 嵌入式系統(tǒng) > 設(shè)計應(yīng)用 > ARM-Linux驅(qū)動--MTD驅(qū)動分析(一)
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          ARM-Linux驅(qū)動--MTD驅(qū)動分析(一)
          
						
          
				作者：
				時間：2016-11-20
				來源：網(wǎng)絡(luò)
				
				
				
				
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			主機(jī)：Gentoo Linux 11.2 with linux kernel 3.0.6
          硬件平臺：FL2440（S3C2440）with linux kernel 2.6.35
          本文引用地址：http://www.ex-cimer.com/article/201611/319012.htm
          MTD(memory technology device內(nèi)存技術(shù)設(shè)備) 在硬件和文件系統(tǒng)層之間的提供了一個抽象的接口，MTD是用來訪問內(nèi)存設(shè)備（如：ROM、flash）的中間層，它將內(nèi)存設(shè)備的共有特性抽取出來，從而使增加新的內(nèi)存設(shè)備驅(qū)動程序變得更簡單。MTD的源代碼都在/drivers/mtd目錄中。
          MTD中間層細(xì)分為四層，按從上到下依次為：設(shè)備節(jié)點、MTD設(shè)備層、MTD原始設(shè)備層和硬件驅(qū)動層。MTD中間層層次結(jié)構(gòu)圖如下：
          從上圖可以看出，原始設(shè)備是MTD字符設(shè)備和MTD塊設(shè)備的抽象。
          MTD設(shè)備層、MTD原始設(shè)備層和Flash硬件驅(qū)動層之間的接口關(guān)系如下圖：
          下面首先分析下MTD原始層設(shè)備
          1、mtd_info數(shù)據(jù)結(jié)構(gòu)
          1. structmtd_info{
          2. u_chartype;//內(nèi)存技術(shù)類型，例如MTD_RAM,MTD_ROM,MTD_NORFLASH,MTD_NAND_FLASH,MTD_PEROM等
          3. uint32_tflags;//標(biāo)志位
          4. uint64_tsize;//TotalsizeoftheMTD//MTD設(shè)備的大小
          6. /*"Major"erasesizeforthedevice.Naïveusersmaytakethis
          7. *tobetheonlyerasesizeavailable,ormayusethemoredetailed
          8. *informationbelowiftheydesire
          9. */
          10. uint32_terasesize;//最小的擦除塊大小
          11. /*Minimalwritableflashunitsize.IncaseofNORflashitis1(even
          12. *thoughindividualbitscanbecleared),incaseofNANDflashitis
          13. *oneNANDpage(orhalf,orone-fourthsofit),incaseofECC-edNOR
          14. *itisofECCblocksize,etc.Itisillegaltohavewritesize=0.
          15. *Anydriverregisteringastructmtd_infomustensureawritesizeof
          16. *1orlarger.
          17. */
          18. uint32_twritesize;//編程塊大小
          20. uint32_toobsize;//AmountofOOBdataperblock(e.g.16)//oob(Outofband)塊大小
          21. uint32_toobavail;//AvailableOOBbytesperblock//每塊的可用的oob字節(jié)
          23. /*
          24. *Iferasesizeisapowerof2thentheshiftisstoredin
          25. *erasesize_shiftotherwiseerasesize_shiftiszero.Dittowritesize.
          26. */
          27. unsignedinterasesize_shift;
          28. unsignedintwritesize_shift;
          29. /*Masksbasedonerasesize_shiftandwritesize_shift*/
          30. unsignedinterasesize_mask;
          31. unsignedintwritesize_mask;
          33. //Kernel-onlystuffstartshere.
          34. constchar*name;
          35. intindex;
          37. /*ecclayoutstructurepointer-readonly!*/
          38. structnand_ecclayout*ecclayout;//eec布局結(jié)構(gòu)
          40. /*Dataforvariableeraseregions.Ifnumeraseregionsiszero,
          41. *itmeansthatthewholedevicehaserasesizeasgivenabove.
          42. */
          43. intnumeraseregions;//擦除區(qū)域個數(shù)，通常為1
          44. structmtd_erase_region_info*eraseregions;//擦除區(qū)域的區(qū)域信息地址
          46. /*
          47. *Eraseisanasynchronousoperation.Devicedriversaresupposed
          48. *tocallinstr->callback()whenevertheoperationcompletes,even
          49. *ifitcompleteswithafailure.
          50. *Callersaresupposedtopassacallbackfunctionandwaitforit
          51. *tobecalledbeforewritingtotheblock.
          52. */
          53. int(*erase)(structmtd_info*mtd,structerase_info*instr);//函數(shù)指針，erase函數(shù)的功能是將一個erase_info加入擦除隊列
          55. /*ThisstuffforeXecute-In-Place*/
          56. /*physisoptionalandmaybesettoNULL*/
          57. int(*point)(structmtd_info*mtd,loff_tfrom,size_tlen,
          58. size_t*retlen,void**virt,resource_size_t*phys);//point函數(shù)功能是允許片內(nèi)執(zhí)行（XIP）
          60. /*WeprobablyshouldntallowXIPiftheunpointisntaNULL*/
          61. void(*unpoint)(structmtd_info*mtd,loff_tfrom,size_tlen);//unpoint函數(shù)與point函數(shù)相反，是禁止片內(nèi)執(zhí)行（XIP）
          63. /*AllowNOMMUmmap()todirectlymapthedevice(ifnotNULL)
          64. *-returntheaddresstowhichtheoffsetmaps
          65. *-return-ENOSYStoindicaterefusaltodothemapping
          66. */
          67. //如果不是NULL，則允許無MMU單元的地址映射，返回偏移地址
          68. unsignedlong(*get_unmapped_area)(structmtd_info*mtd,
          69. unsignedlonglen,
          70. unsignedlongoffset,
          71. unsignedlongflags);
          73. /*Backingdevicecapabilitiesforthisdevice
          74. *-providesmmapcapabilities
          75. */
          76. structbacking_dev_info*backing_dev_info;
          78. //MTD設(shè)備的讀寫函數(shù)
          79. int(*read)(structmtd_info*mtd,loff_tfrom,size_tlen,size_t*retlen,u_char*buf);
          80. int(*write)(structmtd_info*mtd,loff_tto,size_tlen,size_t*retlen,constu_char*buf);
          82. /*Inblackboxflightrecorderlikescenarioswewanttomakesuccessful
          83. writesininterruptcontext.panic_write()isonlyintendedtobe
          84. calledwhenitsknownthekernelisabouttopanicandweneedthe
          85. writetosucceed.Sincethekernelisnotgoingtoberunningformuch
          86. longer,thisfunctioncanbreaklocksanddelaytoensurethewrite
          87. succeeds(butnotsleep).*/
          89. int(*panic_write)(structmtd_info*mtd,loff_tto,size_tlen,size_t*retlen,constu_char*buf);
          91. //用于MTD設(shè)備的OBB數(shù)據(jù)讀寫
          92. int(*read_oob)(structmtd_info*mtd,loff_tfrom,
          93. structmtd_oob_ops*ops);
          94. int(*write_oob)(structmtd_info*mtd,loff_tto,
          95. structmtd_oob_ops*ops);
          97. /*
          98. *Methodstoaccesstheprotectionregisterarea,presentinsome
          99. *flashdevices.Theuserdataisonetimeprogrammablebutthe
          100. *factorydataisreadonly.
          101. */
          102. int(*get_fact_prot_info)(structmtd_info*mtd,structotp_info*buf,size_tlen);
          103. int(*read_fact_prot_reg)(structmtd_info*mtd,loff_tfrom,size_tlen,size_t*retlen,u_char*buf);
          104. int(*get_user_prot_info)(structmtd_info*mtd,structotp_info*buf,size_tlen);
          105. int(*read_user_prot_reg)(structmtd_info*mtd,loff_tfrom,size_tlen,size_t*retlen,u_char*buf);
          106. int(*write_user_prot_reg)(structmtd_info*mtd,loff_tfrom,size_tlen,size_t*retlen,u_char*buf);
          107. int(*lock_user_prot_reg)(structmtd_info*mtd,loff_tfrom,size_tlen);
          109. /*kvec-basedread/writemethods.
          110. NB:Thecountparameteristhenumberof_vectors_,eachof
          111. whichcontainsan(ofs,len)tuple.
          112. */
          113. int(*writev)(structmtd_info*mtd,conststructkvec*vecs,unsignedlongcount,loff_tto,size_t*retlen);
          115. /*Sync*/
          116. //MTD設(shè)備的同步函數(shù)
          117. void(*sync)(structmtd_info*mtd);
          119. /*Chip-supporteddevicelocking*/
          120. //芯片的加鎖和解鎖
          121. int(*lock)(structmtd_info*mtd,loff_tofs,uint64_tlen);
          122. int(*unlock)(structmtd_info*mtd,loff_tofs,uint64_tlen);
          124. /*PowerManagementfunctions*/
          125. //支持電源管理函數(shù)
          126. int(*suspend)(structmtd_info*mtd);
          127. void(*resume)(structmtd_info*mtd);
          129. /*Badblockmanagementfunctions*/
          130. //壞塊管理函數(shù)
          131. int(*block_isbad)(structmtd_info*mtd,loff_tofs);
          132. int(*block_markbad)(structmtd_info*mtd,loff_tofs);
          134. structnotifier_blockreboot_notifier;/*defaultmodebeforereboot*/
          136. /*ECCstatusinformation*/
          137. structmtd_ecc_statsecc_stats;//ECC狀態(tài)信息
          138. /*Subpageshift(NAND)*/
          139. intsubpage_sft;
          141. void*priv;//私有數(shù)據(jù)指針
          143. structmodule*owner;
          144. structdevicedev;
          145. intusecount;//記錄用戶的個數(shù)
          147. /*Ifthedriverissomethingsmart,likeUBI,itmayneedtomaintain
          148. *itsownreferencecounting.Thebelowfunctionsareonlyfordriver.
          149. *Thedrivermayregisteritscallbacks.Thesecallbacksarenot
          150. *supposedtobecalledbyMTDusers*/
          151. //驅(qū)動回調(diào)函數(shù)
          152. int(*get_device)(structmtd_info*mtd);
          153. void(*put_device)(structmtd_info*mtd);
          154. };

          2、mtd_part結(jié)構(gòu)體信息
          1. /*Ourpartitionlinkedlist*/
          2. staticLIST_HEAD(mtd_partitions);//分區(qū)鏈表
          1. /*Ourpartitionnodestructure*/
          2. //分區(qū)結(jié)構(gòu)信息
          3. structmtd_part{
          4. structmtd_infomtd;//mtd_info數(shù)據(jù)結(jié)構(gòu)，會被加入mtd_table中
          5. structmtd_info*master;//該分區(qū)的主分區(qū)
          6. uint64_toffset;//該分區(qū)的偏移地址
          7. structlist_headlist;//分區(qū)鏈表
          8. };

          3、mtd_partition描述mtd具體分區(qū)結(jié)構(gòu)
          1. /*
          2. *Partitiondefinitionstructure:
          3. *
          4. *AnarrayofstructpartitionispassedalongwithaMTDobjectto
          5. *add_mtd_partitions()tocreatethem.
          6. *
          7. *Foreachpartition,thesefieldsareavailable:
          8. *name:stringthatwillbeusedtolabelthepartitionsMTDdevice.
          9. *size:thepartitionsize;ifdefinedasMTDPART_SIZ_FULL,thepartition
          10. *willextendtotheendofthemasterMTDdevice.
          11. *offset:absolutestartingpositionwithinthemasterMTDdevice;if
          12. *definedasMTDPART_OFS_APPEND,thepartitionwillstartwherethe
          13. *previousoneended;ifMTDPART_OFS_NXTBLK,atthenexteraseblock.
          14. *mask_flags:containsflagsthathavetobemasked(removed)fromthe
          15. *masterMTDflagsetforthecorrespondingMTDpartition.
          16. *Forexample,toforcearead-onlypartition,simplyadding
          17. *MTD_WRITEABLEtothemask_flagswilldothetrick.
          18. *
          19. *Note:writeablepartitionsrequiretheirsizeandoffsetbe
          20. *erasesizealigned(e.g.useMTDPART_OFS_NEXTBLK).
          21. */
          23. structmtd_partition{
          24. char*name;/*identifierstring分區(qū)名*/
          25. uint64_tsize;/*partitionsize分區(qū)大小*/
          26. uint64_toffset;/*offsetwithinthemasterMTDspace偏移地址*/
          27. uint32_tmask_flags;/*masterMTDflagstomaskoutforthispartition*/
          28. structnand_ecclayout*ecclayout;/*outofbandlayoutforthispartition(NANDonly)*/
          29. }; 

          
				
            
                
			
							
          
                
			              
              
            
          
		
          
		
          
		
          
		
          
		
          
			
            
				
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